Mikio Yunose returns to his hometown after a six-month absence for studies in Tokyo, where he maintained a long-distance relationship with his childhood friend and former lover, Chitose Yukino, primarily through calls and texts. He arrives anticipating reunion and recalling Chitose's kind, affectionate nature. Visiting the traditional hot spring inn where she serves as young proprietress, he notes her girlish appearance now accentuated by a more mature beauty in her traditional attire.

That evening, searching for Chitose, Mikio follows her voice to an outdoor bath area. Peering through a gap in the bamboo fence, he sees her engaged in an intimate encounter with another man. This discovery shatters his perception of her, plunging him into emotional turmoil and making him question if she remains the person he knew. Fearful that confrontation could permanently end their relationship, he hesitates and doubts, caught between a desire for resolution and apprehension over the consequences. This internal conflict defines his character arc.

In the later spin-off "Hitou Meguri Kakure Yu: Mao-hen," Mikio becomes the object of affection for Mao, who harbors a secret crush. When she invites him on a trip, he accepts. On the train journey, however, he falls asleep shortly after sitting opposite her, sleeping through most of the journey. Mao's subsequent experiences during the trip, including an encounter with another man whose advances are triggered by her feelings for Mikio, unfold without his direct involvement or awareness.