This story would have worked better if the onee-sans weren't all z-cup horny maids. Hard to take emotional scenes seriously when the kid is half buried in tits.
I've seen a lot of crap, but Maken-ki takes the toilet crown for worst anime I've ever had the displeasure of starting back when I binged fanservice battle harems. Far worse than Kuusen Madoushi Kouhosei no Kyoukan, which is barely animated (especially during the god-awful fight scenes) at all...
@JohannesKT Either that or allow summoners to use summons during matches. We've seen that summons can level up and evolve similar to players so it isn't that out of left field.