Shin Megami Tensei X Fire Emblem began with Atlus making a DSi/3DS photo booth app

This information comes from producer Shinjiro Takata…

“I’m not too sure, since this all happened a long time ago. But the way it all started, Atlus was involved with Nintendo when we were making a purikura [Japanese photo booth] app for the Nintendo DSi and the Nintendo 3DS. Then there was a conversation that started about whether Atlus might be in charge of making a new Fire Emblem game. It wasn’t anything serious at the time. I think we turned it down at first because we had too much on our plates.”

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