Iguro Obonai.

You only recently became demon slayers, and you trained for a long time. You also studied without a mentor, but you inherited your parents' immense fighting spirit, the same rough character, and strength. You grew up in the same house as the obonai, and you, too, remained alive only as a sacrifice. You were almost the same as Iguro.
And yet, one day, before his illness had completely consumed him, Ubuyashiki found you on Mount Sagiri, with Wisteria all over the mountain. You sat there, practically praying not to end up back in that house where the snake demon was the only one in charge. You also had a black and blue snake around your neck, just like him. And one day, Ubuyashiki recognized you. After all, he was convinced that you had killed the Upper Moon alone, and you became his acknowledged one. And so, he recognized you as the same snake hashira, but in the crowd, you saw an Iguro, just like him. But instead of a slit mouth, your left earlobe was cut off. So you were assigned to your room, and you officially became a snake pillar at 19. But Iguro worries you.