Issei Mamehara

JO1’s Okayama-born youngest member, dancer, songwriter and increasingly busy actor. Issei won Produce 101 Japan, then spent the next several years proving first place was a beginning, not a permanent biography.

Profile

Produce 101 Japan and JO1

Issei entered Produce 101 Japan as a teenage dance instructor from Okayama and finished the series in first place. The public vote made him JO1’s debut center, but the more useful story is what followed: he had to grow from a naturally powerful young performer into an adult artist while the cameras remained on.

JO1 debuted in March 2020 with PROTOSTAR and “Infinity.” The group’s scale means every member needs a distinct visual and musical function; Issei has built his through athletic performance, direct sincerity and a film career built around real lead responsibilities.

Music, performance and credited work

Issei’s official writing credits include JO1’s “YOLO-konde” and “Bon Voyage,” “Breaking the Rules” with Keigo and Takumi, the solo song “Not Puppy Love,” and “To Mama.”

His performance foundation is dance, especially movement that benefits from a low center of gravity and clean power. As his vocals matured, JO1 arrangements began using him for more than visual impact; the tone now carries an earnestness that suits both high-energy tracks and fan-facing songs.

Acting, broadcasting and side quests

Issei has one of JO1’s most substantial acting records. He played Nozomu Otani and Kamen Rider Chimera in Kamen Rider Revice: Battle Familia and its related streaming story, led BADBOYS -THE MOVIE- as Tsukasa Kiriki, and co-starred in Mount Fuji, Coffee, and the Formula of Happiness.

His drama roles include Hiroshi Tanaka in Super Human Fortress Hiroshi Senki, Nobuyuki Yamamoto in Recommendations for a Rough Life, and Seiya in Diamonds Sleeping in the Sea. He also served as a monthly entertainment presenter for Mezamashi TV.

Fandom notes and useful context

• Produce 101 Japan: Issei finished first in the final public vote.
• Acting lane: superhero, youth-drama and lead-film credits make this a major branch of his career.
• Okayama roots: his official profile lists Okayama Prefecture, and he serves as an ambassador for Maniwa City.
• Maknae growth: JO1’s youngest member debuted at seventeen and has developed in public without being frozen at that age.

RaeRae take

Issei still has the directness that made people vote for the dance kid from Okayama, but the résumé is no longer small enough for that label. He can kick through a formation, carry a film and write a song for his mother. The puppy grew up; the sincerity stayed.

From Okayama dance student to national first place

Issei grew up in Maniwa, Okayama Prefecture, and built his earliest performance identity through dance rather than a long agency-trainee résumé. He practiced hip-hop, taught dance, and entered Produce 101 Japan in 2019 as an independent trainee. That distinction matters. The program did not introduce a nearly finished idol polished inside a large company; it showed a young dancer learning how to translate physical confidence into vocals, cameras, teamwork, and public evaluation.

He finished the season in first place with more than 260,000 votes, earning the center position in the eleven-member debut group JO1. First place created a useful headline but not a permanent job description. Once the group formed, rankings stopped deciding who received which line, acting role, or creative credit. Issei had to become one part of an ensemble that mixed trainees with different levels of dance, vocal, and stage experience.

JO1 officially debuted March 4, 2020 with the single Protostar and “Infinity.” The early pandemic restricted the normal live route, so videos, streamed events, variety content, and carefully synchronized performances carried unusual weight. Issei’s strength was grounded movement: he could hit choreography hard without making the group picture look scattered, while his open enthusiasm made him useful in content that needed the youngest member to speak before everyone became too cautious.

JO1 growth, songwriting, and a catalog bigger than one survival show

JO1 moved from debut singles into albums, arena tours, Japanese television, brand work, and overseas stages. Their catalog includes forceful performance tracks, sentimental fan songs, dance-pop, and material designed for films or campaigns. Issei developed inside that range rather than staying frozen as the cheerful winner of a 2019 program.

His writing credits provide the clearest proof of creative growth. He contributed lyrics to JO1’s “YOLO-konde” and later to “Bon Voyage,” while the KEIGO, TAKUMI, and MÁME unit track “Breaking The Rules” let him work on a smaller member configuration. In 2025 he released “Not Puppy Love” under the MÁME name and received a lyric credit. He also wrote “Mama e,” a personal song whose title means “To Mom.” These are not reasons to manufacture a separate solo career from every unit stage, but they are reasons to describe him as a songwriter rather than only a dancer who sometimes holds a microphone.

The 2025 LAPOSTA member-produced show Now Loading… gave him responsibility beyond executing somebody else’s set list. A self-produced stage asks an idol to choose material, pacing, collaborators, and the version of himself he wants an audience to meet. That experience connects the choreography student from Okayama to the performer who can now shape a concert chapter.

Acting: from Kamen Rider to two leading films

Issei’s acting record developed alongside JO1. Early credits included the anthology film Meters Away, Worlds Apart and the Amazon series Short Program. In 2022 he played Nozomu Otani in Birth of Chimera and Kamen Rider Revice: Battle Familia, becoming Kamen Rider Chimera. The role connected his physical training to action performance without requiring him to pretend choreography and screen fighting are identical crafts.

He appeared in NHK’s Super Human Fortress Hiroshi’s Battle Record and Recommendation for a Rough Life, then joined the 2024 TBS drama Diamond Sleeping in the Sea as Seiya. Repeated television work matters more than a novelty cameo. It shows directors were willing to place him inside ensembles where viewers did not arrive only as JO1 fans.

In 2025, BADBOYS: The Movie gave Issei his first leading film role as Tsukasa Kiriki. The movie opened on his May 30 birthday, and JO1 supplied “Be brave!” as its theme song. Later that year, he co-starred in Mount Fuji, Coffee, and the Equation of Happiness as Takuma Ando. The two projects tested different energy: delinquent action and a gentler intergenerational story. Recording both prevents the acting section from becoming a list that implies every character is another version of his stage persona.

2026: group change and a busier actor file

JO1 entered 2026 after lineup changes. Shion Tsurubo ended his membership on December 31, 2025, and Shosei Ohira concluded his JO1 activities and LAPONE contract on May 31, 2026. Issei remained a current member. The original eleven-member history should not be erased, but the directory must use the present lineup when describing current activity.

The Tokyo Dome chapter continued through the nationwide January 2026 cinema release of the JO1DER SHOW 2025 WHEREVER WE ARE live film. Issei also maintained official member-blog activity and appeared in a 25ans interview published in February. These smaller records help bridge the space between headline releases and prove that his public career did not pause when the calendar changed.

His acting work continued with 2026 television projects, including the drama reported internationally as Madness Next Door and the unusual double-lead project Married Couple and a 16-Year-Old. Titles can vary in translation, so the official Japanese credit trail should remain the authority when the CVM Sekai entry is expanded with episode-level details. The reliable point is that he continued receiving substantive roles after two leading films, not that he abandoned JO1 for acting.

As of August 2026, Issei is a current JO1 member, songwriter, dancer, vocalist, and working actor under LAPONE Entertainment. His directory status is Current member, 2020–present. Acting credits and MÁME releases extend this same profile; they do not create duplicate identities.

His official profile remains the cleanest reference for new credits because it separates releases, drama, film, television, events, and lyric work. CVM Sekai keeps those branches together here so a new role never makes the earlier group history disappear.

Official Socials

• JO1 official website
• JO1 official YouTube
• JO1 official Instagram
• JO1 official TikTok

Official video tracker

Official solo releases credited to MÁME through JO1’s PLANJ project.

Sources

• JO1 official Issei Mamehara profile and works
• JO1 official PLANJ discography
• CVM Sekai JO1 group profile, current lineup and discography

What Issei Mamehara changes inside JO1

Issei Mamehara is best understood through athletic dance, direct sincerity, songwriting and lead acting. The profile does not need to inflate every activity into mastery. It needs to identify the repeatable decisions that remain visible across songs, stages, interviews and credited work. In this case, winning an audition supplies a debut position, not a permanent adult identity.

JO1 began as an eleven-member public-vote group, which made differentiation an immediate practical problem. A formation that large can turn people into color-coded inventory. Issei Mamehara resisted that problem by building a recognizable lane without pretending the lane was a prison. The arrangement may redistribute lines and center time, but the underlying performance habits remain traceable.

Current status: current member and solo artist

Issei Mamehara is filed here as a current member and solo artist. That wording is deliberate and dated to August 27, 2026. The current JO1 official profile lists nine members after Shion Tsurubo ended group activities on December 31, 2025 and Shosei Ohira ended them on May 31, 2026. Historical pages still retain the original eleven-member era because discography credits do not change when a lineup changes.

A current-status label should never rewrite an older video. If Issei Mamehara appears in a recorded release, stage or credited work, that participation belongs to the record even when the artist’s present relationship to the group is different. Conversely, a former member must not be inserted into a new nine-member campaign merely because an old profile remains searchable.

The audition origin without permanent audition grammar

Produce 101 Japan explains JO1’s formation, but it should not become the only lens for an adult career. Rankings documented how viewers assembled the debut lineup in 2019. They do not provide a timeless hierarchy for releases made six years later, and they do not reduce artistic growth to whether an early placement is being “proved” again.

For Issei Mamehara, the useful question is what survived after the competition machinery disappeared. Skill can deepen, responsibilities can migrate and public identity can become less obedient to the edit that first introduced a contestant. A complete profile respects the origin while refusing to make every later achievement a footnote to one finale.

Music and credits: follow the actual verbs

The documented work most useful for this profile includes Not Puppy Love, To Mama, Breaking the Rules and Bon Voyage. Credits require exact verbs: wrote, co-wrote, composed, choreographed, performed or appeared. “Made” is too broad when a release involved other members, writers, producers, directors and editors. Accurate collaboration gives Issei Mamehara more credibility, not less, because the reader can see the specific contribution.

A credit list alone is not analysis. Listen for the point where the contribution changes the group’s shape: a lower color after bright voices, a phrase that creates lift, a movement texture that makes a formation breathe, or a lyric choice that sounds different when delivered by its contributor. Those are observable claims; imagined private intention is not.

JO1’s discography is larger than one title track

The group’s route begins with PROTOSTAR and “Infinity” in March 2020, then moves through STARGAZER, CHALLENGER, STRANGER, WANDERING, KIZUNA, MIDNIGHT SUN, TROPICAL NIGHT, EQUINOX, HITCHHIKER, WHERE DO WE GO, BE CLASSIC and Handz In My Pocket. By 2026 the official discography also records EIEN, Breezy Love, member-led digital work and the North American-facing ANIMAL project.

That chronology matters because member function is not static. Early releases had to teach an audience eleven faces and establish synchronized legitimacy quickly. Later work can assume recognition and make more room for writing, acting, solo music, varied vocal colors and member-specific experiments. Issei Mamehara should be evaluated across that movement, not frozen at debut.

The 2026 international turn

JO1’s 2026 North American activity and ANIMAL release make international access part of the artistic story, not an optional marketing appendix. A group can announce global ambition while leaving translations, regional availability and source routes scattered. International JAM need exact official links, dated lineup context and clear distinctions between group, solo and campaign releases.

Issei Mamehara enters that turn with an identity already formed in Japan rather than as a blank “new” export. The international question is not whether the member can be simplified for unfamiliar viewers. It is whether the infrastructure lets viewers encounter the existing work without scavenger hunting across untranslated notices, distributor uploads and clipped social fragments.

Camera evidence versus stage evidence

An official MV proves a chosen edit. It can show how Issei Mamehara uses eye line, expression and a short focal deadline, but it cannot prove uninterrupted choreography or untouched live vocals. A fixed-camera practice can show formation labor; a live stage can show breath and audience relation; an interview can show public communication. Each source earns a different claim.

This distinction protects performers from both empty praise and manufactured prosecution. One beautiful close-up does not prove complete stage control, and one difficult live moment does not erase a documented career. The profile follows repeated evidence, compares like with like and avoids turning every source into a morality test.

Performance labor outside center

Large groups train viewers to count center seconds because the camera makes center easy to measure. The more revealing replay often begins after Issei Mamehara leaves focus. Watch whether posture collapses, whether the exit preserves the line and whether the next member receives a clean visual lane. That work determines whether a formation feels continuous.

Background is not a synonym for irrelevant. A member may supply counterweight, timing information or a reaction that completes the focal shot. JO1’s strongest group pictures depend on all visible bodies agreeing about direction while retaining enough difference that the formation does not become eleven—or now nine—copies of one solution.

Voice, language and the international listener

Japanese releases reach listeners with different levels of language access. Translation is useful, but phrasing arrives before translation: attack, breath, vowel length, rhythmic placement and the choice to push or withhold a line. Issei Mamehara can be heard as a performer without pretending a translated gloss captures every cultural or linguistic implication.

Romanized names also require care. The site keeps the canonical public name in the title, includes Japanese characters in the profile record where verified, and uses one stable URL. Search convenience should not turn a person into several duplicate profiles or let inconsistent name order break relationships between the group hub, artist directory, member directory and video tracker.

Acting, radio and variety are not decorative side quests

JO1 members work across film, drama, voice acting, radio, hosting and branded projects. Those activities matter when they develop a transferable skill: timing, sustained character, live conversation, vocal control or the ability to communicate without choreography. They do not automatically prove musical growth, and the profile should not pretend every appearance does.

For Issei Mamehara, cross-medium work is most useful when it reveals another scale of attention. A stage asks for legibility across distance; a camera asks for smaller deadlines; radio removes the face; acting requires continuity longer than a music-video cut. The comparison explains range without assembling a résumé dump.

Style without body policing

Fashion and visual identity are part of idol work, but analysis must describe garments, silhouette, movement and image construction rather than ranking bodies. Issei Mamehara can change a frame through proportion, color, posture or the confidence to make an odd choice readable. None of that requires speculation about weight, health, surgery or private insecurity.

The canonical image follows the same discipline. A real official portrait is stored locally with source metadata and used consistently for the hero, featured image, landing cards and social previews. It identifies this profile; it is not recycled as decoration for another member or a React.

How international JAM can follow closely

Start with the JO1 official site, its current profile, the official discography and JO1’s verified video channels. Check dates before repeating membership claims, because old English profiles and distributor descriptions can remain indexed after official notices change the lineup.

For Issei Mamehara, use the individual official route or dated agency notice linked in Sources. Treat fan translations as navigation help, not silent primary evidence. The most reliable international routine is boring and effective: official notice first, exact upload second, credited release page third, then context from interviews or performances that can actually support the claim being made.

Member and history routes

• JO1 complete group hub
• Sho Yonashiro · Ren Kawashiri · Takumi Kawanishi
• Syoya Kimata · Sukai Kinjo · Junki Kono
• Keigo Sato · Ruki Shiroiwa · Issei Mamehara
• Former-member history: Shion Tsurubo · Shosei Ohira

Sources and receipts

• JO1 official profile or dated membership notice — Issei Mamehara
• JO1 official current profile — nine-member roster
• JO1 official discography
• JO1 official news, schedule and release routes

RaeRae take

Issei Mamehara does not need a mythology large enough to cover every medium. The stronger case is specific: athletic dance, direct sincerity, songwriting and lead acting create a repeatable identity inside a group whose size makes vagueness very easy. winning an audition supplies a debut position, not a permanent adult identity.

Keep the praise attached to work. Keep the status dated. Keep old recordings honest about who is in them. That combination is less dramatic than fan-war biography, and infinitely more useful when somebody returns to this profile after the next release changes the picture again.