do u guys know this manga?

I've read a manga b4 about this mc i think he was isekaid and he transmigrated into the body of a fat guy and people didnt like him n stuff cuz i think the orig owner of the body was a bad guy and there was this school event and one of the prize was a potion and the mc rlly wanted cuz it can help him. I think the manga also involves some magic. im sorry thats all i can remember since its been so long