Yui is a female customer who made her first appearance in Papa Louie 3: When Sundaes Attack! She's a fan-made customer chosen by fans in Kingsley's Customerpalooza 2014. She was created by Facebook user Júlia Diabliková.
Yui has a long, brown hair split into two braided ponytails. She wears a green beanie, a green and brown-striped tank top, a brown skirt, bracelets on both wrists, and tan shoes with brown soles and laces. She also carries a brown travel bag.
- Yui is the first customer to debut in a platformer game after Papa Louie: When Pizzas Attack! and the first customer to be a playable one in a platformer.
- The weapon she uses is a crossbow with long spoons for arrows, which are from Papa's Freezeria.
- She is not considered a new customer in Papa's Cheeseria since she debuted in Papa Louie 3: When Sundaes Attack!
- On QWERTY and AZERTY keyboards you can read their name on the keyboard, because the letters "Y", "U" and "I" are continuous.