Coming back to Devil Survivor 2: Record Breaker is the Demon Auction mechanic, which is the main way to acquire new demons (that and fusing of course).

Devil Survivor 2

Each demon has a certain rating -- the more stars the better stats and skills it comes with, meaning a strong ally for immediate use, or eventual fusion ingredient later on. There's also special auctions for exceptional demons but you'll need plenty of Macca (the in-game currency) for those.

Watch the trailer below to see how the auctioning process works.