I'm with xyzzy (i didn't post anything though). I thought it would have more of a mystery side to it. I'm very much into weak main characters having to deal with despair inducing situations, so having the magic ball suddendly appear and it becoming a let's just kill the monsters is indeed kinda disappointing...
That said, i still quite enjoy a lot of "let's just kill the monsters" type of mangas too, so it's not that big of a deal... People just have to accept that, since it's not them that are writting the story, it'll sometimes not go the way they want.
Also, to Snowmanne... what are you even talking about? this doesn't resemble GATE in the slightest... Gate takes a way more political aproach to the interaction between worlds, this... doesn't even mention another world, and the sole interaction is immediate killing, the statues don't even show any form of communication. There is no "pacifist constitution" on this too... they're fighting against statues for all they know... no one is hesitating on killing statues. The JSDF didn't oversight things, it's not a independent organization, it responds to government. The author just had it fail due to burocratic reasons, on taking too long for government to respond to such sudden catastrophe.