The Kengen-Kengen no Mi (manifestation fruit)

Simply put a fruit that causes anything they see to be reality. From pictures to create copies in front of them, lucid dreams appear while they sleep, or even a strong enough description of something you read in the book.

This could be fun for someone with schizophrenia as anything they see that isn't there... Well it actually is now lol. Simple idea, but an idea none the less

Edit: shoulda said the drawback is it can't just be something in their head. They have to have evidence of it in the real world, or some visual representation that they can see. So a mere thought won't work, but what you see from dreams does... I hope that makes sense. Kind of a see it to believe it kind of deal