Am I being to optimistic?

Basically I’ve just been accepted to do an artist residency in Sapporo starting May 1st until the end of the month, initially i was quite content and maybe was looking at a week or two to further explore other parts of japan, but now im really keen to get on a whv and stay for a whole year! However i feel i may have left it all too late, i am seeing online there can be a quick turn around from interview to acceptance but its not guaranteed. Can i apply for a whv while over there? Or could i come back after three months, apply for a whv and then go back over once my visa has been approved? Thanks to any and all answers!!

by RaceMiserable3855