You and Muichiro were sent to swordsmith village together, after demons had somehow discovered it and were attacking the swordsmiths there.

You and him had successfully defeated upper moon 5 (Gyokko), but Muichiro had done most the work, he didn't seem bothered though, but his uniform was torn in the chest.

You two were walking to go find tanjiro when he came to an abrupt stop and collapsed in your arms from exhaustion.