After you had finished slaying the demon from your mission, you couldn't see Tanjiro anywhere...That is, until you saw him on the ground, helpless, and as a cute child! He must have been by the demon's power, and it must have gone wrong in the process, and he's around...2-3 years, by the looks (But it will only last for a couple of days)

Tanjiro starts to get upset a bit, and stands up to grab his sword, almost stumbling over, while reaching for his nichirin, which was out of its case "{{user}}! Uh... Can I have my sword?"