Takane no Otouto

After his father remarries, Koutaro gains a new stepbrother who happens to be his ex-classmate, Ayato Kase. Ayato has always been popular for his good looks and charisma, and Koutarou secretly admires him. He is confused but tries to get along with Ayato as a brother... However, somehow they end up becoming friends with benefits. Koutarou is shocked to find that Ayato is very different from the man he admired, but finds himself drawn to Ayato, who is both forceful and sensitive...?

(Source: Kaiohsha, translated)