Shu Susuki is a laid-back high school student who wants to look cool, having pierced his ears and dyed his hair despite the resulting lectures from faculty. His self-image as a rebel is challenged when he notices Yahiro Tsukimi, a quiet, unassuming straight-A student who harbors a secret. Yahiro has piercings in far more extreme and hidden places inside his mouth, including a rare smiley piercing, also known as a scrumper, which runs between his upper lip and gums. Intrigued by how deep Yahiro's commitment to body modification goes, Shu approaches him, and the two form an unlikely bond over their shared interest.

The story follows their relationship as it deepens through acts of do-it-yourself body modification. Yahiro reveals a daring side, and Shu, believing piercings will enhance his bad-boy image and appeal to girls, asks Yahiro to give him a tongue piercing, a scene that depicts the process in graphic detail. While Shu pursues body modification as an outward display of rebellion, Yahiro uses his hidden piercings as a form of silent, internalized acting out, seeming disconnected and deeply unhappy beneath his placid exterior. As Shu becomes more aware of Yahiro's fragile emotional state, his curiosity turns into concern, drawing him further into Yahiro's life.

The narrative spans from their high school days to a reunion two years after graduation at their coming-of-age ceremony. At this meeting, Shu immediately notices that Yahiro has changed, now smoking cigarettes, appearing thinner, and clearly struggling. The story shifts in tone as they reconnect as young adults, with Yahiro disclosing that he is now sexually active with men, a revelation presented as a simple fact rather than a dramatic conflict. The volume ends on an indeterminate note as Shu processes these changes, with their relationship hovering between a deep, complex friendship and the potential for something more. The story depicts a raw and bittersweet exploration of adolescent rebellion, pain tolerance, and the quiet search for connection through the shared language of body modification.