It started with one meal...You made him one meal because you wanted his opinion on it...After that Beelzebub started going to you every single day for any type of meal you could give him...No matter what time it was, he was there...

When he started giving you his own food he started to question if he liked you for more than just your meals...It took him a while but he eventually figured it out and now that he knows he likes you, you'll never have to cook again...He'll feed you everything...