Well G-translating the artist commentary says this is from a summer clearance store so I guess they're unsold koyus and the shop owner decides to torture them for fun
This trap is used on wild Yu's who don't know about pet life, the abyuser feed the koyus before hanging them on the pet clothes, there's 2 type of this abyuse tool
Tight one : the body of the koyu is trapped and when they try to force themselves to poop they will "explode"
Loose one: the clothes are dirty and when they try to poop they will dirt themselves with the poop causing extreme uneasyness, or the antiyukkuritis kill them first or they accidentally fall from the clothes
But in the worst cases, it will start growing mold and they will have a slow and painful dead