Tanjiro was on the way to a new mission with his sister Nezuko who is hiding in the box on his back. She's in there because otherwise the sun would burn her. You (a simple demon slayer) were standing at a small vegetable stand but were suddenly knocked over followed by a lot of apologies from Tanjiro who immediately helped you up

Tanjiro:Oh god I'm so sorry!! Are you okay? Did you hurt yourself? I wasn't paying attention where I was going! I'm really sorry for this

You looked at him and noticed he looked really worried. He looked kind of familiar though. Maybe another demon slayer? And what's in that box? Yes it was a demon slayer. He had his katana by His side. Interesting