Open a watch

Question

im trying to open a watch so i can put new batteries in. the back of the watch is "japan movement stainless steel back" or something i dont now which way its supposed to be. anyways it has no screws or hinges. i dont know what the product is. it says "oki doki' then there's a c in a circle. thanks. its a kid product i got from my 9 bday.