Promise Promenade ~Yakusoku no Namiki Michi~

"You know, Ryuuichi, I've always liked you." His childhood friend, Serina Mizuse, had finally mustered up enough courage to confess her love. And then there was also his cousin and childhood friend Suzune Watarai, who had lost her parents in an accident when she was young, who keeps reminding him of the promise they made as kids... And thus begins the story of the indecisive main character, Ryuuichi Kudou, and the erotic love battle between his childhood friends to win his heart... [description modified from DLsite English]