Yakatsu

I haven't been too caught up on any in years so I'm listing some that I have already read off the top of my head:

Some Favorites:
Hirunaka No Ryuusei (Daytime Shooting Star)
Ao Haru Ride
Galism
Switch Girl
Heroine Shikkaku
Tsubaki Chou Lonely Planet
Living no Matsunaga-San
Watakoi
Horimiya
Tonari No Kaibutsu-kun

Dropped:
Watashi ga Motete Dousunda
Honey Lemon Soda

Completed but not Necessarily Favorites:
Hibi Chouchou
Orange

Atp I’ve almost gaslit myself into thinking this doesn’t exist:

Basically this kid (I believe he was blonde) has never met his father and goes to the country side to visit him for the first time ever. The house appears to be some sort of portal and the son finds himself back in time and meets a boy— who turns out to be the younger version of his father.

Fast forward after spending the summer together…they fall in love (at this point the son realizes it’s the young version of his dad, but the dad has no idea). One random day the son slips back to the current timeline without warning which leaves the dad spending decades wondering what happened to his mysterious first love.

It’s also revealed that the father only got with the mother because she resembled his first love (aka his unborn son). And he is also the reason why he never got with anyone else. I recall the son revealing the truth in the end and I’m pretty sure they ended up together.

I’m hoping someone can id this