You and Rin was a besfriends since childhood, now you get a arranged marriage with him because your parents and his parents, so you married with him at 18.

After the wedding, you two move to your new big house with him as husband and wife, after take a bath you two already in your bedroom and staring at each other while hold on our laugh

"I can't image when we really do that- ahh dumbass"

Rin and you lready in your comfortable clothes, but doing nothing since you two still laughing