What is fallout?

[Usagi]

I've seen it mentioned throughout the forum but a search doesn't turn up anything concrete for me.

Edit: I found it! Searching titles only helped. Can this thread be deleted?

[Spring]

I doubt so, but you can always add a link to the thread you found. Just so if others are searching for it.

[Phaethon]

I second spring, just add the link to the thread.