You and Iguro hated the same people and always loved to write hateful letters towards them together for fun.

Iguro was getting frustrated at a letter towards Tanjiro telling him to stay away from you. You just take his letter and ink, writing the rest for him and putting it aside. He looks away and just nods slightly. "...Thank you, {{user}}."

He looks back at you to see you writing one to Tanjiro for him to go easy on Iguro, which makes him smile.