Actually, its like the father will be the only one to remember him( the son in law). The father went back being teenager, maybe he will grow old as time passed, and growing old he’s the only one to remember the (son in law) because realistically, the (son in law) was not yet born or still baby (maybe) when the father was young thats the (son in law) cant remember him, but the ( father in law) remembers him. That’s why if you check in previous chapters, the ( father in law) seemed to know the ( son in law) already, and maybe I don’t they fell in love before and promised something but the son can’t remember and decided to marry the step daughter so the father is disappointed.
Or it can be that the father will go back being old, and ofc the memories will be there. But everything happened will be erased in the memory of the son.since remember the teacher of son’s brother? Like they’re into something.
Sorry i tried :(
Yep not equal was it, it was a trip LOL
http://www.mangago.zone/read-manga/not_equal/
Im starting to understand the 1st chapter as to why the father in law went to him to clean his teeth ( older version) i cant explain but I think i know