Ohh... sorry. I had been playing the PC versions on the night I made that post, so I was thinking about those. I forgot that you were playing on Vita.
I can't say for Shun because I don't have that (or any other PS1 game, actually) on Vita, but for the original Umihara Kawase, no, unfortunately it's not possible to change the controls, other than the lure/jump buttons.
Sorry again for my mistake.