Naisho no Otonari-san

Rino Kasuga, a high school girl who loves cooking, moves to Tokyo from a rural mountain village. Her next-door neighbor in the apartment building, Kaoru Todo, looks just like a yakuza...! One day, she helps Todo, who has collapsed in front of her house from hunger, and ends up cooking for him on a regular basis...?

(Source: Hakusensha, translated)