Daikichi Kawachi is the central protagonist of the story, a 30-year-old bachelor whose life is redirected by an unexpected act of compassion. At the outset, he is depicted as a fairly ordinary, hardworking single man with a stable job at a clothing company, but his life lacks a sense of deeper purpose. He has a tendency to be seen as gruff or intimidating, which has historically made him somewhat awkward around women and children. His lifestyle before becoming a guardian is characterized by a certain carefree irresponsibility, including smoking, drinking, and dedicating most of his energy to his work.

Daikichi's personality is a blend of awkwardness, gentle sincerity, and quiet determination. While he is initially portrayed as being not particularly fond of young people, this is less about genuine dislike and more a result of inexperience and a lack of exposure. His defining characteristic is his straightforward and honest nature, which manifests as a powerful sense of responsibility and empathy. At his grandfather's funeral, he is moved to anger by his relatives' cold and dismissive treatment of the deceased man's illegitimate young daughter, Rin. Seeing her as an unwanted burden being casually discussed for placement in an orphanage, Daikichi makes an impulsive, life-altering decision: he announces he will take the child in himself.

His motivations, initially a product of moral outrage, quickly solidify into a steadfast dedication to Rin's well-being. He is driven not by any grand ambition, but by a simple, resolute desire to do the right thing for a child who has no one else. This becomes his primary purpose. He admits to a coworker that raising Rin requires sacrifice, but his actions demonstrate that he views this not as a burden, but as a commitment he willingly chose. His motivations extend to creating a stable, loving home, which he pursues with a practical and humble approach, constantly learning from his mistakes.

In the story, Daikichi's role is that of an adoptive father and guardian, a role he steps into with no prior experience. He is the emotional anchor of the narrative, and his journey of learning to be a parent is the core of the story. He navigates the daily challenges of childcare, from enrolling Rin in a kindergarten to dealing with her fears, illnesses, and social development. To better care for her, he makes a significant professional sacrifice, requesting a demotion from his successful position in the sales department to a lower-stakes role in logistics. This change, while a step back in his career, allows him the regular working hours necessary to pick up Rin from daycare, demonstrating his willingness to forfeit professional advancement for his domestic responsibilities.

His key relationships are central to his development. His bond with Rin is the heart of the story, beginning as a pact between two strangers and deepening into a powerful, genuine parent-child connection. He learns to read her quiet, sensitive nature, and she, in turn, brings warmth and purpose to his formerly solitary life. Another significant relationship is with Yukari Nitani, a divorced mother of Rin's friend, Kouki. Yukari becomes an invaluable mentor and confidante, offering Daikichi guidance and reassurance when he doubts his parenting abilities. A subtle, unspoken romantic tension develops between them, built on mutual respect and shared experience as single parents, though Daikichi's own uncertainty prevents him from acting on these feelings for a long time. His bond with Kouki also grows into a close, almost father-son friendship, as Daikichi becomes a reliable male figure for the boy, someone who offers both guidance and discipline.

Daikichi undergoes significant development throughout the narrative. He evolves from a somewhat disconnected bachelor into a mature, selfless, and devoted parent. This transformation is neither sudden nor easy; it is a gradual process of trial and error. He learns to manage a household, cook, and understand the emotional needs of a child. He confronts his own shortcomings and insecurities, often seeking advice from others without letting his pride get in the way. By willingly giving up his carefree lifestyle, including smoking and late nights out, and accepting a less glamorous job, he demonstrates a profound shift in priorities from personal ease to familial duty. His journey is one of finding profound meaning and joy in responsibility and love, fundamentally reshaping his identity from a single career man to a dedicated father.

Among his notable abilities is his remarkable resemblance to his late grandfather in his youth, a physical trait that initially helps the frightened Rin feel a sense of familiarity and trust towards him. While not possessing any extraordinary skills, Daikichi's most notable ability is his quiet, stubborn resilience and his talent for creating a stable, secure environment through sheer, consistent effort. He has a practical, problem-solving approach to parenthood, patiently working through each new crisis, from finding a daycare with open availability to dealing with bedwetting, without complaint or melodrama.