Reddit users on r/PSP have shared various homebrew versions, though some report these versions may be incomplete or missing dialogue. PSP ISO Emuparadise: Free Downloads & How To Play - Ftp
Which of those would you prefer?
: It is possible to install Undertale on Android devices or tablets using wrappers, which provides a similar "handheld" feel to the PSP. PSP Top Picks (Official RPGs) undertale psp iso download top