Movie
Description
Yuzuhiko Tachibana, the younger son in the Tachibana family, begins the series as a second-year junior high student. His name follows the family's citrus theme, complementing his sister Mikan. The family lives on the fifth floor of a Tanashi, Nishitokyo apartment building.

Naturally studious and forward-thinking, Yuzuhiko often devises clever solutions to family problems, displaying intelligence beyond his years. He possesses a picky and strict nature, particularly concerning household manners, and readily criticizes family members for carelessness. Despite this, he demonstrates responsibility and a nurturing side while babysitting his young neighbor Tatkun, engaging in play while teaching life lessons.

At home, Yuzuhiko prefers solitude in his room, emerging primarily for meals. He bristles at excessive maternal attention and rejects the childhood nickname "Yuu-chan," desiring to be treated as an adult. Contrastingly, his school persona is free-spirited; he is popular with peers, enjoys joking with friends like Fujino, and performs teacher impersonations, highlighting his comfort in social settings outside the family.

His hobbies include playing video games, listening to music, and a secret admiration for the fictional idol Marumi Maruno. He discreetly collects her photos and memorabilia to avoid ridicule. Yuzuhiko is also particular about food, especially mayonnaise brands, and occasionally engages in imaginative role-playing, such as pretending to be a bar chef while cooking.

Relationships define his experiences. His closest friend, Fujino, shares interests in books and games but often acts immaturely, creating a comedic dynamic; Fujino's crush on Mikan causes Yuzuhiko discomfort. Other friends include timid Nasuo, sociable Sudou, and quirky Yuri Ishida. A notable subplot involves classmate Sayu Kawashima, who harbors a crush on him and forms a "Fan Club" (calling him "Hibari-chan"). Her attempts to confess feelings frequently falter, sometimes due to Ishida's interventions. A misunderstanding over an unflattering doodle Yuzuhiko drew of Kawashima briefly cooled her affections, though reconciliation followed after he clarified his intent.

Throughout the series, his character evolves as he navigates social complexities like handling crushes and maintaining friendships, balancing his dual identities—reserved at home and expressive at school. The sequel *Shin Atashin'chi* further explores his school interactions and minor interests, including his culinary role-playing.