Mei Tachibana is the protagonist of the story, a sixteen-year-old high school student who has built walls around herself after a painful experience in her past. She lives a quiet life with her widowed mother and her beloved pet cat, a large white feline named Marshmallow. Her father passed away from cancer some years before the story begins, leaving a quiet absence in her family life.

Mei’s withdrawn nature is a direct result of a traumatic event during her elementary school years. She was falsely blamed by her classmates for the death of the class pet, an incident of betrayal that led her to conclude that forming close bonds with people is a recipe for inevitable hurt. In the years that followed, she adopted a solitary existence, avoiding friendships and romantic relationships to protect herself. Her classmates perceive her as gloomy, quiet, and anti-social, and she is often the target of their teasing. Despite this, Mei possesses a quiet, unshakeable honesty and is surprisingly observant about human nature, often offering blunt and insightful observations that others might miss. She is also notably independent, insisting on paying her own way and rarely asking for help.

Underneath her cool and distant exterior lies a shy, clumsy, and easily embarrassed young woman. She is more comfortable around animals than people, but her innate kindness and non-judgmental nature act as a quiet magnetism that gradually draws others to her. As she becomes more secure, she develops a fierce loyalty, willing to stand up for herself and, more importantly, for her friends when they are wronged. Her character is defined by a significant journey of growth. Initially terrified of being hurt again, Yamato Kurosawa becomes the first person she learns to trust. As he patiently chips away at her defenses, Mei begins to question her long-held beliefs and slowly opens her heart, learning to navigate the complexities of friendship and first love. Her development is a gradual process of learning that vulnerability is not a weakness, and that connection, despite its risks, is worth the potential pain.

Her role in the story is centered on this transformation. The narrative follows her as she moves from a self-imposed isolation to a life filled with meaningful relationships. The most significant of these is with Yamato Kurosawa, the most popular boy in school, whose persistent kindness and affection force her to confront her fears. Their relationship begins in an unconventional and chaotic manner and evolves into a deep and committed partnership that, in the source material, eventually leads to marriage and starting a family. Through Yamato, she meets and befriends others. Asami Oikawa becomes her first female friend, a relationship that teaches her the value of same-sex trust and support. Aiko Mutō is initially jealous of Mei’s relationship with Yamato but eventually becomes a close and fiercely protective friend. She also clashes with Megumi Kitagawa, a manipulative rival who sees Mei as an obstacle to winning Yamato’s affection. Her empathy allows her to connect with others who share her sense of loneliness, such as Kai Takemura, a boy from Yamato’s past with a history of being bullied, and Nagi Kurosawa, Yamato’s younger sister who fears being abandoned. Beyond her emotional strengths, Mei has a few notable abilities. She is surprisingly talented at bowling, an unexpected skill that emerges during a group outing. She is also known for her large appetite, particularly when she is feeling stressed or angry, and she always carries bandages with her, ready to use them on anyone in need.