It's covered in the first 10~20min or so of the game, and is really a minor side point.

Off topic, put P5 as a game doesn't really care about spoilers much, there is one specific story telling gimmick that will screw with you if you're really sensitive to these kind of things.

It's not really a spoiler. It is something that happens near the beginning of the game.

If I am not mistaken, it's even shown in the marketing materials to build suspense.