Yankee ni Koi to Ikuji wa Muzusugiru

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)