omg i'm so curious about that absolute duo thing because amazing animation in the OP but also angry because,,, ECCHI HAREM TRASH
omg, i know it looks tempting, but please don't bother because the OP animation is nice but the actual show-animation is like. sub-par because all the detailed animation points all go into boob jiggling frames.
But, uhh absolute duo is about a battle royale type school where people have ~soul weapons~ that damages the soul rather than the physical body. the main character guy's weapon isn't really.. a weapon. he manifests a shield which makes him irregular. the silver haired girl is one of those socially helpless badass moe types and they pair up (basically everyone in the school pairs up to form duos). the girls in the show are actually lovely to each other and supportive but if only to add some male-gazey lesbian flair in the future, I think.
nothing really makes sense?? i would recommend watching soul eater instead, since it sorta has the same premise, but it's just the better, slightly less gross anime.