Kawaikereba Hentai demo Suki ni Natte Kuremasu ka?

One afternoon, after finishing his cleaning duties in the Calligraphy Club room, Kiryuu Keiki discovers an anonymous love letter addressed to him resting on a desk. Thrilled by the prospect of finally finding romance, he eagerly opens the envelope, only to find a brief confession reading "I like you" tucked alongside a pair of women's panties left behind by the mysterious sender. Armed with nothing but this highly unconventional piece of evidence, Keiki is forced to deduce the identity of his secret admirer from the small group of girls who helped him clean the club room that very same day. His list of suspects includes four distinct candidates: Tokihara Sayuki, the laid-back third-year president of the Calligraphy Club; Koga Yuika, a library committee member of foreign descent; Nanjou Mao, a slightly tsundere classmate; and, most awkwardly of all, his own younger sister, Kiryuu Mizuha, who happens to be an obsessive neat freak. Convinced that the panty-leaving admirer is among them, Keiki resolves to investigate each girl closely. With unwavering determination, he sets out to uncover which of these seemingly unorthodox young women orchestrated such a scandalous confession, hoping to turn this bizarre mystery into a genuine relationship.