Watashi no koto, Netotte Misete

"An NTR manga featuring a weak-willed and naive protagonist and a manipulative girl. Kurashiro Shion is a pitiful high school student who obsessively pines after Kira Hinano, the cunning and heartless girl in their class. Kira takes advantage of Kurashiro's loneliness by bonding over shared hobbies, all while toying with his emotions. When Kurashiro finally confesses his love, Kira cruelly reveals that she already has a boyfriend, shattering his self-esteem and dismissing him without a second thought. Left devastated and isolated, Kurashiro remains emotionally broken, while Kira continues to enjoy her superficial popularity, showing no remorse for her actions."