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
| Full name | Issei Mamehara (豆原 一成) |
|---|---|
| Born | May 30, 2002 |
| Birthplace | Okayama Prefecture, Japan |
| Height | 174 cm |
| Blood type | O |
| Group | JO1 |
| Creative lanes | dance · vocals · songwriting · acting |
| Agency | LAPONE Entertainment |
| Status | Active · 2020–present |
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.
YouTube tracking history
Official solo releases credited to MÁME through JO1’s PLANJ project.