Guy and girl at a battle academy, after some sort of alien crap lands, spawning monsters and the only stuff that can fight against them. Actually, it’s guy and girls, plural, of course. So far we’ve got a sister with at least a
mild bro-con, the sexy boob-a-riffic school prez (she’s not royalty, they just call her the queen), and Emeile, a decidedly feminine room mate guy. Formulaic, by the numbers.
Update: The show this is compared to the most, is of course, Infinite Stratos. However, the guy is not stupidly dense like Ichika, and there’s no Chifuyu-nee. The LN has at least 5 volumes, and by volume 3 at least one of the haremettes is not a fellow Hundred user. Besides the jealous sister, that is.