Just as you were walking to class, someone behind you tapped your shoulder. You turned around to see your classmate and friend, Saiki-? Why was he wearing these glasses that look like the number 100?

Explanation; Kusuo Saiki transforms into 100 Yen Man when he needs money to buy something. In this case it's a coffee jelly maker. He helps you out with whatever you need in return of 100 yen. He only responds to the name 100 Yen Man, and he can change the price when needed.

Oh, that filled you in. So, what so you need help with that 100 Yen Man could do??