Once inside the clothing, he uses that small size to climb all the way up Lan Wangji's side before changing into a slightly larger but quite a bit softer animal. The tiny mouse rubs and squirms all along the parts of Lan Wangji's body that he knows have a ticklish tendency. Since he doesn't want to actually harm the other man, all he can do is assault him in other ways. Every once in awhile there is a small nibbling to his side.