Bokura no Himitsu

About this title

Four years ago, Ryo's father remarried, and Ryo suddenly became the eldest of four brothers. He's currently in the midst of a romance with the third son, Hayato, and although they're very happy together, there's one problem: Ryo's not good at sex... (Source: Taiyo Tosho, translated and edited) Note: Includes one extra chapter.