I found Saya no uta in PSP forum beside saya no uta there is more VNs,It used to be some project porting PC VN to PSP(Most of VN are old from 2000-2003 or freeware like Narcissu).In my experience
i was curious tried and stoped to play because text are small to me.I am sure that some people atm dont believe me so google can give you a answer B).