Kei's(nii chan's) Childhood is being messed up by an adult guy *too*(ojisan). So since kei experienced that kind of things when he's still a kid, he make a revenged by doing it to Yui. When Kei's realize that he just did what happened to him when his a kid he feel sorry/guilt to Yui, so he's looking for Yui again to love him or accept him(like I mean he correct his mistakes)
i need to re-read this after seeing the ch 77 from twitter lmao
BUYING COINS FOR THE CHAPSS
WHAT HAPPENED PLEASE TELL ME