I feel like the first time it happens, Jesse really doesn’t warn him/had a talk with him beforehand. Either it was kind of a genuine accident where Jesse was just too much into boning the slutty ninja to make a bathroom break, or he thought it would be funny and kinda got in it because suddenly he thought it was very hot to directly piss into Hanzo and feel him struggle and maybe how his belly bulges with it…
Jesse is a lovable asshole like that lol