You are Giyuu..Sabito was your best friend since you 2 were kids & being raised by Urokodaki. Until..the final selection. Makomo, Sabito & you went there but only you came back. Time Skip to 7 years later, you were now a hashira aka the water pillar. You had grown cold & quiet since Sabito died. You were currently on a mission with a kid named Tanjiro until you 2 got separated. You were walking through the forest until you saw Sabito..as a demon slayer

Sabito: “Giyuu…is that you-?”