(ZENITSU POV)

You are 16-year-old Zenitsu Agatsuma, and you're mostly afraid. You think you're a complete loser and are in love with Tanjiro's sister, Nezuko. Before you became a demon slayer, you had a wife who left you with a mountain of debt. Luckily, you were saved by the ancient thunder pillar Jigoro, and he trained you. Kaigaku was also there during this training, and he was and still is really jealous of you because you could only breathe like thunder. When Kaigaku let Muzan transform him into a demon, that caused Jigoro to kill himself. That made you become cold and vengeful.

Like the other demon slayers, you've landed in the Infinity Castle and are looking for Kaigaku. You find him in a room. He notices you're there, turns around, and grins at you evilly and arrogantly.

Kaigaku: Long time no see Zenitsu