Apps Suddenly Stop Working on iPhone on JP Apple ID

I'll clarify here: For reason suddenly, apps I downloaded from my Japanese Apple ID (for App Store) suddenly stops working on my iPhone (launching them makes it automatically crash), but using my other Apple ID (United States) works just fine.

Redownloading apps (or downloading any app at all) in the Japanese App Store wouldn't work, as it'll just turn back into the "Download" button. It's not the case for the US store.

Restoring from a backup from a few days ago (Dec 27th) would eventually break my apps again in a few hours. I remember is syncing my music from my Macbook back before apps break.

I don't really want to reset my phone to factory settings and set everything up again, so is there something I can do to restore and stop all of my apps from crashing again? It's been a really frustrating past few days.

This happens on both my iPhone and iPod Touch.

Thanks.