If I may ask, what kind of clothes do the vampires wear in the pet au, since they have special designated clothes, and what would the s and m boys wear?

Admin Mawile: ~ヾ(＾∇＾)

-Vampires, considering how human they look, have to at least be kept modest. Most are given old, poor quality articles of clothing, like simple pants or wraps, and are commonly given just enough to be kept modest. When they have different roles, like show or house pets, they can have fancier outfits, but the average pet will be dressed in just enough to consider them presentable. Collars or some mark of identification is common, though. 

The Sakamaki are probably on the nicer side of pet clothes. They’re from a respectable breeder, and are kept looking decent in the hopes that someone will purchase them. They probably wear clean, simple pants and shirts, without any kind of unnecessary decoration, but neat enough that they look properly dressed. When shown off to potential adopters, they may get nicer things. 

The Mukami, however, are from a pretty horrible environment. The best they probably get is a pair of dirty, tattered pants; just enough to be modest, and without wasting any “unnecessary” money on them. They’ve probably never worn anything nice in their lives, and once their on their own on the streets, they’ve kept the same, old pieces of clothing for years.