Based on a game by Lune TeamBitters.

Masaharu and his fiancée Sayaka are preparing for their wedding. Masaharu's sister Misato is taking care of the planning and preparations together with her lover Kaneko Ryuuji whom they have known since college. Everything seems to be going fine, however Ryuji takes an interest in Sayaka after seeing her in her wedding dress. When Masaharu is busy and unable to attend one of their meetings due to work Ryuji takes advantage of his absence and begins to make Sayaka his...