Everyone here's well accustomed to rough living on the road, right? ...not Kaiba, so much, because he's new. And the thing about the dangerous life in Hisui is that all that running through grass and mud stains clothes quickly. Kaiba is also training an exceptionally affectionate and exceptionally slimy Goomy, and that makes the need for efficient clothes-washing an urgent one.

He's building something along the lines of this, upscaled to fit a handful of loads at once...and Zephyra the Ponyta is getting better at providing small flames, so water heating is handled.

(he is very irritated about this new life and channeling his frustrations between training sessions into building)