Mayuta Andō, a former motorcycle gang leader, abandons his delinquent life after an encounter with Chio Miyamo during her school commute. When Chio accidentally knocks over his bicycle and adopts her online persona "Bloody Butterfly" to intimidate him, her deception successfully compels him to leave gang life.

He takes legitimate employment as a convenience store clerk and develops unwavering romantic feelings for Chio. His persistent efforts to gain her attention involve exaggerated and absurd gestures, including studying female erogenous zones and referencing boys' love game tropes under the mistaken belief that Chio enjoys such content. These actions lead to misunderstandings regarding his sexuality.

He has a younger sister, Chiharu Andō, who seeks to identify the "Bloody Butterfly" figure she credits for his departure from gang life. Chiharu mistakenly believes Manana Nonomura holds this influence, unaware of Chio's role. Mayuta exhibits protective instincts toward Chiharu, defending her against perceived threats even while unconscious.

His romantic pursuit of Chio includes multiple confessions. An ambiguous declaration in chapter 33 is misinterpreted by Chio as a comment about a life buoy, though she visibly flusters. An unambiguous confession in chapter 43 results in mutual acknowledgment of feelings, establishing them as a couple.

Transitioning from delinquency, he becomes an earnest yet frequently misguided individual striving for normalcy and romantic connection. His interactions often feature comedic misunderstandings or over-the-top gestures aimed at impressing Chio, reflecting his ongoing adjustment to conventional life.