Tortoise Matsumoto is a Japanese singer, songwriter, and actor who is recognized as an original creator within the anime and manga field, primarily for his work on the anime series Waimo-kun~Kiiroi Kao Shite Babanban. Born Atsushi Matsumoto on December 28, 1966, in Hyogo Prefecture, he is best known as the lead vocalist for the rock band Ulfuls. His educational background includes attendance at the Osaka College of Design, a foundation that has contributed to his visual creative work.

Matsumoto’s role as an original anime creator stems directly from his personal artwork. He based the character Waimo-kun on sketches he originally drew around 1989 on concert advertising flyers for Ulfuls. These flyer sketches featured a character with a yellow face and speech balloons containing the phrase "Wai mo!," an Osaka dialect expression meaning "Me too!" The character gained recognition among Ulfuls fans, eventually becoming a mascot for the band. This fan adoption and his own attachment to the character led to the creation of the anime short series Waimo-kun~Kiiroi Kao Shite Babanban, which premiered on the Music On! TV satellite channel on October 6, 2009. For this project, he was credited as the original creator, with Yuichi Fukuda handling series composition and Tomohisa Ishikawa directing.

Beyond his work as a creator, Matsumoto’s musical career has intersected with the anime industry through contributions as a composer. His band, Ulfuls, performed the second opening theme song, "Baka Survivor," for the anime series Bobobo-bo Bo-bobo. His music composition work also extended to the second season of the anime Mr. Osomatsu, where he participated as part of the collaborative project ROOTS66 Party, contributing to the ending theme "Let’s Go! Muttsu Go! 6 Shoku no Niji" in 2017.

Matsumoto’s artistic identity in this context is characterized by a crossover between his musical performance career and his personal visual art. The creation of Waimo-kun represents a direct translation of his informal, fan-engaged sketches into a formal animated work, establishing a distinct connection between his work as a rock musician and his identity as an anime originator. His significance in the industry lies in this multivalent creative role, demonstrating the path from fan-created mascot to officially produced media, a trajectory grounded in his established public persona as a prominent figure in Japanese rock music.