Gokudou no Shokutaku

Recently divorced Raizou Kuji is the head of a yakuza organization and is involved with illegal businesses on a daily basis. But being single at the age of 55, he has to cook for himself and being the foodie that he is, just any kind of dish will not do. On top of that, Raizou starts attending night school with people half his age, with no idea that he is a leader of the feared yakuza. He has to keep this a secret from his much younger classmates all the while managing dangerous men capable of highly illegal activities.

(Source: Mangahelpers)