When i checked the rating after watching this i was shocked to see just 7.1,
it really deserves more really really more, it has a fantastic screen play with more than a decent story line and an excellent character development,
The quality of the animation is beautiful picture perfect you can say.
I don't know why it is so underrated, probably the reason for this is the story line being bit too confusing in the initial stage, That's the only reason i can come up with.
Initially you really won't understand what's happening, what and why are they attacking each other, which is a good side and which is not, Anyway moving forward things will start picking up and you will get proper clarity for all that has happened and what is happening,
it may not give you any anxiety or a high level curiosity but still It is an interesting anime,
The only suggestion i can give you is not to get frustrated with the initial episodes.