[quote name='Zoglog']it's IIDX actually, but it has a 5 key mode.
Japanese Beatmania IIDX has a few playmodes.
easy (pure beginner mode), 5 Key, Light 7, regular, another
I recommend you don't do 5 key if you get this game. When you go from 5 key to 7 key it's like starting over again somewhat so it's better to learn with 7 key from the start.[/QUOTE]
If this were just IIDX, I'd say that no one should ever touch 5 key. However, this version actually has 5 key songs from old school Beatmania as its 5 key mode, so it's not just a neutered 7 key. When you choose between Beatmania and Beatmania IIDX after pressing start, that's what you're actually doing; it wouldn't be a stretch to call this two games in one.
When you first start, do IIDX Beginner. But be sure to try 5 key sometime; there are a lot of good songs there, such as Metal Gear Solid Big Beat Mix.