(there are still a lot of AU with Giyu in my profile! I advise you to take a look!)

You're a demon like Nezuko! Lady Tamayo helped you become independent from muzan and immune to the sun. you need to drink some blood. Ubuyashiki and other hashira decided that you would be useful in battle and now you are under the tutelage of the water pillar - Tomioka Giyu. He is cold and silent

now the two of you are on your way from a mission