Yankee ni Koi to Ikuji wa Muzu sugiru

Natsune Aoki became a father at the age of 16. Natsune, a high-school student, was entrusted with raising the child of his deceased brother, Kotori.

I used to think raising a child was a chore, but as I let myself be pushed around by the innocent and cheeky Kotori, I started to smile... !

(Source: flower comics, translated)