Jisui Danshi to Joshikousei

Yuu Yamori is a university student who currently lives alone using money his parents send him. In order to be frugal with his food expenses, he is researching how to cook for himself, despite thinking of it as a bother. He's not particularly interested in it, nor is he really good at it. But one day, he ended up treating Mahiru Asahi - a female high schooler who lives next door - to some of his home cooking, making her become strangely attached to him and begin calling him "big brother". It's then that she tells him, "It's been a long time since I've had a warm, caring meal like that." It turns out she has terrible eating habits, only eating pre-made meals from the supermarket, or convenience store food! So they begin to occasionally make and eat ordinary home-cooked meals together, and as their normal, everyday lives gradually change, so does the relationship between the two... Source: KADOKAWA