It just leaves you hanging with Rin training to beat the main bad guy.
No closure of any sort.
Does she get revenge for him killing her parents?
Does she finally get the attention of Manji?
Go read the manga suckers!!!
Well, I guess in these manga -> anime cases there are 3 options:
- make a non-ending anime and perhaps release a second season/series at a later date
- make an anime-original ending
- wait for the manga to (almost) finish before starting the creation of an anime
All 3 of those options are sure to annoy some
(AKA: a lose-lose situation for longer manga. Well, a "win" situation would be to produce manga fast enough, resulting in the anime never catching up to the manga before the manga finishes...)