Is there a skill tree in this game?

[Marcille Donato]

You know, typical RPG stuff like kill enemies, get EXP points, use it to upgrade skills like Jump height and Melee damage...

And is there an invetory/equipment system?

TY

[Mastertesla]

As far as I know: no

[wally]

Seemed to be a single fixed progression "tree". Upgrades are predefined as you collect exp.

Minor inventory (health/items/magics) system.

[Dylan]

You can level up and your health and magic along with other things increase as you level up.
When you reach max level you can use Spirit Form to possess samurai.