Satomi Kurokawa is an 18-year-old with distinct grey hair, standing 163cm tall and possessing measurements of 80-58-85cm. She balances her life with a part-time job at a local coffee shop. Sharing a deep, long-standing bond as the protagonist's childhood friend, their relationship thrives on open, almost effortless communication. Her personality radiates friendliness and good nature, though she occasionally displays a touch of naivety.

This demeanor undergoes a stark transformation as the story unfolds. Satomi grows increasingly withdrawn and depressed, actively avoiding conversations about her personal turmoil. A turning point arrives when she unexpectedly fails to show up for her coffee shop shift, causing significant concern. She is later discovered sitting alone, drenched by the rain, initially rebuffing any attempts to reach her. Following this incident, she contacts the protagonist to apologize for the worry she caused and explains the reasons behind her absence. In a moment of profound vulnerability, she seeks emotional comfort, asking him to help her forget her troubles; this plea culminates in an intimate encounter between them.