Joshima features solely in the series' adaptation of "Run, Melos!". As the childhood friend of protagonist Takada, they once planned to move together to Tokyo—Takada aspiring to be a writer, Joshima a performer. Yet Joshima remained in their hometown for undisclosed personal reasons, an act Takada viewed as betrayal. This abandonment fueled Takada's lasting resentment and emotional pain, fracturing their bond.

Years later, terminally ill and on his deathbed, Joshima summons Takada home. Their reunion unveils Joshima’s original sacrifice: staying behind to ensure Takada could freely pursue his Tokyo dreams, echoing the Greek fable of Melos that Takada adapted. In his final moments, Joshima enables their reconciliation. Takada realizes Joshima had silently championed his ambitions despite their separation. Joshima’s death concludes his arc, resolving the core conflict—whether it is more agonizing to wait or to make another wait—through his experience: awaiting Takada’s success while confronting mortality.