Boku wa Shitteiru.

A high school student named Sunao notices a salaryman on a bus, whose ring finger bears hidden teeth marks. Curious about their origin, Sunao becomes consumed by thoughts about the man. Later, they meet again at Sunao’s part-time job at an izakaya, where the salaryman, after drinking, confronts and kisses him. The intense emotions between them are not yet love, but something raw and complicated. The story follows their relationship, and a later extra chapter explores their connection after the main events.