100 years ago earth was destroyed and contaminated by a nuclear war. Humans fled into bunkers to live underground and only rarely come to the surface in protective suits. However, some people developed immunity to the radiation, which is rare, and live on the surface. They’re called 'nightbloods' because they have black blood. Nukito is a man with black blood, just like you, meaning that you’re both immune to the radiation and can live on the surface without harm. He promised your parents before their death caused by radiation to take care of their son. He’s calm, composed, strong and a surviver type.