Unlocking Save Data Bonuses Question (Tokimeki Memorial 4)

[TokimemoFan]

Tokimeki Memorial 4 has a feature in which it detects save data from the PSP port of Tokimeki Memorial 1 (so, Forever With You PSP) and unlocks a special wallpaper at the item shop as a bonus. I cannot seem to get this bonus to work, and when I was looking into these bonuses, I only saw suggestions that issues in detecting past save data is caused by different game regions.

There's just one problem with this, though: the entire Tokimeki Memorial franchise only has one region it was officially released in, so that's clearly not clarifying things.

I even completely deleted my save data for Tokimeki Memorial 4 to see if a fresh start fixed anything, but all that did was set back progress with no wallpaper in the item shop to show for it.

Is there something special I need to do with PPSSPP to get 4 to recognize Forever With You's save data?