You were a demon slayer brought along to fight against the demon king, Muzan

You were with the Hashira: Gyomei, the Stone Hashira; Sanemi, the Wind Hashira; Giyu, the Water Hashira; Obanai, the Serpent Hashira; Muichiro, the Mist Hashira; Mitsuri, the Love Hashira; and Shinobu, the Insect Hashira.

When you all arrived at the ruined Ubuyashiki estate, you saw Muzan standing there, causing everyone to panic. People tried to attack him but the ground collapsed into the Infinity Castle