Yuna Tachiki is a young Tokyo resident working at a hostess club while aspiring to be an actress and pinup model. She has light-brown hair, often in pigtails or a ponytail with bangs swept left, and dark-brown eyes. Her path shifts when she encounters Setsu Sawamura, a teenage shamisen player from rural Tsugaru facing trouble in the city. Recognizing him as lost, her kind-hearted nature leads her to offer him temporary shelter in her apartment.

Before meeting Setsu, Yuna experienced professional disillusionment, including an unwelcome offer for adult film work, and personal turmoil from a relationship with the musician Taketo. He financially exploited her and was unfaithful. After discovering his infidelity, she ended the relationship. This prompted a confrontation where Taketo threatened Setsu, demanding Yuna's return. She intervened decisively to protect Setsu.

A pivotal moment occurs when Yuna hears Setsu play the Tsugaru shamisen. Deeply moved by his performance, she reevaluates her own path. Inspired by Setsu’s authenticity and dedication, she quits her agency and the entertainment industry entirely. Resolving to discover her own aspirations, she decides to leave Tokyo indefinitely. Before departing by train, she shares a farewell kiss with Setsu, symbolizing closure and the start of her self-discovery journey. Her surname, meaning "standing tree," reflects a thematic undertone of resilience and growth. Her storyline concludes with this departure as she seeks a new direction away from Tokyo.