I think RevStu once said that Raiden doesn't have a story at all, which is awesome if true. The enemy invaders have a name, though, so presumably there's at least the outline of a conflict established on an arcade flyer somewhere. Bah.
Anywho, I've finally got around to playing Eschatos, and it's absolutely wonderful. Just pure concentrated joy.
Listen to that bloody music. I love the way the game is broken up into distinct 10- or 20-second waves of enemies - the complete destruction of which you're rewarded for with multipliers and bonus points - even though it's essentially one continuous level. It feels old-school and completely fresh at the same time; some of the enemy waves look like they should be in some Galaga remake, but they're integrated into this frantic barrage of different ideas, different ways of attacking you and keeping you on your toes. The crazy on-the-fly perspective changes take some getting used to, but you have a recharging shield that you can activate by holding the two shot buttons, so you can always just use that while you're getting used to them. It has loads of modes, too - Original and Advanced each have several difficulties with their own leaderboards, as well as an 'Endless' variation which lets skilled players loop the game as many times as they can, whereas Time Attack mode times you on taking out enemy waves, and punishes you by deducting seconds rather than lives when you get hit. There's an awful lot to do.
It also comes with Judgement Silversword and Cardinal Sins. And you get to choose your WALLPAPER BLIGHTNESS. It's altogether far too much of a bargain. You should buy the Wonder Price version on Play-Asia. You can kiss me later.