I have a feeling that the manga is going to end at the same spot as the first season, so I wouldn't let the fear of getting too invested stop you from finishing it. It actually does end at a fairly decent spot, kinda like the Fruits Basket anime. You know that there's more to the story, but it's still a pretty satisfying ending for the arc, regardless. (Not that it stops me from wanting to see the second season. :P)

Somebody should license the novels, so we can get the WHOLE story. That would be awesome!