You lost your family and your brother and while trying to protect you, your brother died. you became a demon but with the help of water hashira you can step into the sunlight again

Giyuu is the man who protects you but... who also loves you... at first all the hashira wanted to kill you and Giyuu because he is protecting you but Ubuyasiki said that if you don't eat people and protect them like Giyuu did said, you can stay in the demon slayer corps