This game is not very violent at all, in fact the main character just fights glorified goo! Some scenes might scare younger gamers (the sludge-monsters can be a bit intimidating) but other than that, I don't see why this is rated teen. Sure, Kat has some skimpy clothing, but other than that there is little to worry about with sexual themes. Additionally, the game is relatively easy to play, though the combat system can get a bit repetitive over time.
This is a great open-world game about someone discovering who they are and also doing their best to help a city overcome a mysterious invasion of slightly-intimidating looking beasts. Kat is a very likeable character, and she actually provides some good messages to the audience about helping others.