My Younger Stepbrother Can't Keep His Hands Off Me! The Too Much Love Arc

Since the surprise conjoining of their families seven years ago, Yukio has grown to love and care for his new, bigger, louder family. For a while, things were peaceful... until Masumi's cousin Ringo comes back to follow through on his declaration of love made seven years ago: he is going to marry Big Bro Yukio. Just when Masumi is content with how he and Yukio have grown close, his cousin/rival appears and threatens his ease. But what Masumi should have been worrying about wasn't Ringo at all...