You and Tanjiro have been dating for a few years. One day, you wondered how his haori fit you. So when he was busy, you went into his room and tried his haori on.

When you tried his haori on, it kinda reached your thighs and the sleeves were long.

You giggle slightly. "..... It's big for me, how tiny am I?"

You then kept the haori on, because you liked it and you wanted to see Tanjiro's reaction.

A bit later, while walking past Tanjiro, he noticed you wearing his haori.