Twenty-nine-year-old Kanon works as a shojo manga artist, coasting through a life that feels half-finished in both career and romance. That precarious balance shatters when her older sister and brother-in-law are killed in a traffic accident, leaving behind their five-year-old daughter, Neiro. Unmarried and with no experience raising a child, Kanon nevertheless steps forward to take in her orphaned niece, uprooting her Tokyo life and moving into a modest apartment to start over.

Kanon is immediately overwhelmed. She is grieving her sister, her long-term boyfriend Yuki grows distant and argumentative, and her manga deadlines pile up. Five-year-old Neiro, meanwhile, is a quiet, gentle girl who has lost everything she knows. The two struggle to find a rhythm: Kanon loses her temper when Neiro acts out, and Neiro retreats into herself, unsure of the aunt who is suddenly her guardian.

Their new home sits next door to two young men. Shinichi Miyama is a calm, observant neighbor who works a mysterious job and seems to have a difficult past of his own. Yoda Rikuto—often called Rikkun—is warm and sociable, quick to offer help with errands and childcare. Neither is a blood relative, yet both gradually become fixtures in the makeshift household, acting as ersatz father figures and support for Kanon when she stumbles.

The early narrative tracks Kanon's steep learning curve as a single guardian: navigating Neiro's first days at kindergarten, juggling deadlines with parent-teacher meetings, and learning to forgive herself for the moments she fails. Season by season, the apartment becomes a quiet hub of what the manga calls a pseudo-family—an aunt, a niece, and two unrelated men who share meals, celebrate holidays, and fill the roles of mother and father even though none of them truly are.

Tension builds as Yoda proposes they become a real family, pressuring Kanon to define what that means. At the same time, Miyama's hidden profession comes to light, threatening the fragile trust they have built. The fourth volume introduces a sports festival, a Christmas celebration, and a turning point when Yoda falls ill and Kanon must decide how much she is willing to let these people into her life—and her heart.

The story unfolds as a slow, warm domestic drama focused on found family, the weight of sudden responsibility, and the shared efforts of people who are not related by blood but who choose to care for one another anyway.