Hiroto Honjo is a reserved and pragmatic high school student. He maintains a childhood friendship with Saki Akutsu, who lures him to Aya Chiyono's week-long birthday camping trip at an abandoned factory with a false claim of needing to discuss something important. Feeling "dragged along," Hiroto attends reluctantly. This reluctance fuels his consistently grumpy and critical attitude toward the group's activities.

He cultivates a studious image, often seen reading books that suggest intellectual depth. However, this proves a facade; the books are actually adventure novels. Significant pressure from parents prioritizing academic achievement dominates his home life, breeding deep-seated resentment. This resentment erupts in anonymous online posts on a secondary account, where he expresses extreme frustration, including statements like wishing his "shitty parents would die" and criticizing their singular focus on his studies. These posts later become public, causing social fallout.

During the factory stay, Hiroto voices practical concerns about consequences. He worries about Aya's father's reaction to her disappearance and cautions against sheltering Malet, the undocumented child, warning it constitutes criminal complicity. His cautious nature starkly contrasts with the others' rebellious enthusiasm. When the students' identities are exposed, Hiroto faces personal scrutiny. His past online posts are discovered and disseminated, leading to public criticism labeling him disturbed and potentially dangerous. More recent posts criticizing the group's actions as childish and singling out Saki's sentimentality are also revealed, causing her visible distress.

A turning point occurs during the group's emotional confessions. Hiroto confronts his own dissatisfaction, admitting he lives entirely dictated by his parents' expectations and expressing self-hatred for his compliance. This vulnerability marks a significant shift from his earlier cynicism. He also forms an unexpected bond with Souma Ogata, a classmate bullied in middle school. Hiroto reassures Souma his past doesn't matter to their friendship and expresses genuine anticipation for future activities together, like playing baseball. This interaction reveals his capacity for loyalty and a desire for authentic connection, moving beyond his initial aloofness.

His development culminates in the dismantling of his carefully constructed facades—the false intellectual image and the emotionally detached attitude—revealing a more complex individual grappling with familial pressure and a yearning for self-determination.