"Marriage Blue" is a steamy hentai OVA series following Masaharu and his conservative fiancée Sayaka as they prepare for their wedding, only for complications to arise when Masaharu's sister's lover, Ryuuji, becomes obsessed with Sayaka after seeing her in her bridal gown. When Masaharu misses a planning meeting due to work, Ryuuji seizes the opportunity to seduce the innocent bride-to-be, drawing her into intense, forbidden encounters that challenge her purity.