キスはないしょに

Ayumi Kyono, a high school freshman, gains a new stepbrother, Takeru Kase, when her father remarries. Takeru, handsome and popular with girls, constantly receives phone calls, which unsettles Ayumi. Despite being in the same grade, Takeru’s earlier birthday makes him her “older brother,” complicating her growing attraction to him. As they adjust to living together, Ayumi grapples with her feelings, questioning their appropriateness given their sibling status. Their daily interactions in a typical high school setting spark moments of tension and budding emotions. (Unreviewed summary by Grok 3)