Fūto is the twelfth son of the Asahina family and a first-year student at Yōdai High School. At fifteen years old, he leads a dual life as a popular student idol, a career he has pursued since childhood. This early immersion in the entertainment industry has significantly shaped his outward demeanor, granting him the verbal polish and self-assurance of someone much older, yet often expressed through a brash and cheeky arrogance.

Personality-wise, Fūto is best described as a mischievous and self-assured individual. He carries himself with a natural, almost theatrical, charm that captivates his fans, but at home, this persona often gives way to a more teasing and provocative nature. He derives a great deal of amusement from unsettling those around him, with his new stepsister being a primary target of his verbal barbs and suggestive jokes. This behaviour is underpinned by a strong sense of self-reliance and a desire to be in control of any situation, rarely showing vulnerability. Despite his provocative exterior, he possesses a serious and professional side, approaching his work as an idol with a rigorous dedication and passion that contrasts with his casual attitude at home.

Motivation plays a key role in his actions. While he publicly enjoys the fame and attention, his core drive is a genuine ambition to become a professional actor, a goal he pursues with near-obsessive determination. In the context of the family, his motivations are more complex. His initial treatment of his new stepsister appears to be a form of entertainment for him, enjoying the way she reacts to his teasing. However, as the story progresses, this playful torment evolves into genuine romantic interest, creating a significant internal conflict as he navigates his feelings against the backdrop of their sibling relationship.

Within the narrative, Fūto serves as a source of disruptive energy and romantic tension. His arrival at Yōdai High School surprises his stepsister and his brother Yūsuke, immediately escalating the sibling rivalry between them. He frequently toys with Yūsuke’s feelings for her, accusing him of having improper thoughts and delighting in their arguments over her attention. His relationship with his stepsister is the most pivotal; he often calls her his beautiful idiot sister and takes pleasure in flustering her with flirtatious comments and physical closeness. This dynamic reaches critical points where he acts on his impulses, including an instance where his brother stops him from kissing her and another where he considers taking advantage of her while she sleeps, only to stop himself after realizing the depth of his true feelings for her.

Fūto’s development is subtle but significant. He begins as a character who simply toys with emotions for his own amusement, seemingly dismissing his step-sister as uninteresting. Over time, his perspective shifts as he recognizes her beauty and her unwavering, sisterly commitment to the family, which both frustrates and attracts him. A notable turning point occurs when, after being reminded of her desire for them to remain a family, he is moved to tears and retreats, demonstrating a capacity for emotional depth and restraint that his earlier behaviour would not have suggested. His primary abilities are not physical or supernatural, but social and performative; he is a talented singer and actor capable of completely transforming his public persona into a gentle and charming idol, a skill he deftly wields to manipulate social situations to his advantage.