It's more of a 'collectathon' platformer than an action game... Not the most visceral experience around, but it's dripping with style and has great presentation.
Each level has a few objectives to consider:
-Accomplish whatever primary objective finishes the level(Kill a certain foe, reach the exit, etc...it varies)
-Destroy enough of the environment to release hidden souls trapped within trees, walls, jars, houses(ie. the collecting) You can re-visit levels as much as you desire to fulfill this requirement and continue breaking stuff. Game saves your progress, so you don't have to re-destroy everything if you are looking for that last standing tree somewhere.
-Unlock hidden weapons/spells/items by performing -optional- bonus objectives in each level. (Beat in 3:00, land a 700-hit combo, etc...) You pretty much need a faq to figure out what these hidden objectives are, but the rewards are usually nice and the challenges are generally enjoyable.
It's a pretty cool game, but the combat lacks depth. You can equip 40 or so weapons, but they all function the same outside of elemental and stat properties. You will spend most of the game using the exact same button string over and over. It is quite beautiful though, and worth a playthrough.
Supposedly Otogi 2 is quite overhauled.