Keita Torigaya stands as Ryo Washizu's sole initial companion before Washizu expands his social circle. Across both anime and manga adaptations, Keita begins with a masculine presentation but experiences a gradual physical metamorphosis, growing noticeably smaller and developing more feminine features over time. Only Washizu perceives this transformation, with other characters remaining oblivious to the shift. The anime unveils Keita's female gender abruptly in its final episode without prior context. The manga, however, approaches this revelation incrementally, offering its first significant clue in chapter 37 when Keita dons a maid outfit during a cultural festival. The narrative provides no explicit rationale for the physical changes or gender disclosure.

Keita consistently exhibits a cocky, arrogant attitude toward Washizu, frequently engaging in lengthy monologues that irritate him. Despite this behavior, Keita displays authentic affection for children, revealing a nurturing dimension. The character's background—including family, age, or motivations—remains unexplored. Keita's role centers exclusively on interactions with Washizu, never expanding into broader storylines or meaningful connections with other main characters. The physical evolution and gender revelation function solely as comedic or surprising narrative elements, devoid of deeper character exploration.