Ryuu Tachibana served as Kentarou Yamamoto's right-hand man within the Inugane yakuza group until a major operational failure resulted in forced sex reassignment surgery as punishment. This transition created Mari Tachibana, who became one-third of the idol group Gokudols.

As Ryuu, Mari exhibited a dandy appearance, formidable fighting skills, and deep admiration for actor Hitoshi Takamura—collecting films and later attempting unsuccessfully to offer herself to Takamura post-transition. Personal preferences included a strong dislike for sweets that dissolved a past relationship. Post-surgery, Mari retained masculine mannerisms and struggled with idol life, experiencing jealousy over uneven fan attention toward fellow members. Health complications from the surgery, particularly recurring hemorrhoids and anal afflictions, occasionally led to public incidents.

Mari's transgender father initially rejected the transition but later reconciled. Post-surgery development involved reluctant acceptance of idol duties amid internal conflict between yakuza instincts and feminine performance. Mari adopted a "cool" persona in Gokudols but sometimes reverted to crude language or violent impulses under provocation. A live-action film subplot featured Mari forming a relationship with a lesbian nurse treating surgery-related complications.

The character arc emphasized Mari's uneasy, gradual adaptation to femininity—occasionally embracing fan interactions or feminine-coded gifts despite resistance. The duality of yakuza loyalty and idol performance remained central, with Mari supporting fellow members during crises while navigating identity struggles.