The world where suddenly 7 angels appeared from the sky and caused supernatural events, where some people suddenly got mysterious powers
Our MC is named Takanari Shirou.

From MangaHelpers:
Summoned into an alternate world of Alayzard, Ousawa Akatsuki helps defeat the demon lord, brings harmony back into the world and, under the demon lord’s last request, takes the demon’s only daughter back into Akatsuki’s own world.
It turns out that being teleported into a different world is somewhat of a common occurrence back home. Those who return often come back with the power to use magic. So a worldwide organization, fearing people like Akatsuki, created Babel, a school to teach and keep tabs on the magic users.
Akatsuki is able to bring the demon lord’s only daughter into Babel as his sister, Ousawa Miu. A new chapter for Akatsuki is about to begin--this time, in his own universe!

First year high-school student, Toujo Basara, is now living with two beautiful step-sisters thanks to his eccentric dad. But Mio is actually the new Demon Lord and Maria's her succubus chaimberlain. Throw in a "reversed contract," rival demon tribes, and the ecchi situations mainly brought on by Maria for good measure, and you have a situation where Basara's life will never be the same. This seinen adaptation of the light novel mostly focuses on the said latter ecchi situations that occurs between the three main characters.

"Hey, you said you wanted a sister, right?" First year highschool student, Toujo Basara, was suddenly asked by his father and fell into a state of panic. On top of that, the eccentric father told him he will be getting remarried. He then departed overseas after bringing Basara two beautiful step-sisters. But Mio and Maria's true forms are actually the newbie Demon Lord and a succubus!? Basara was almost entered into a master and servant contract with Mio, but a "reversed" contract was formed by mistake, and Basara is now the master!? Moreover, Basara is being hit by ecchi situation one after another due to the contract, but Mio's life is being pursued by other demon tribes and hero tribes!! The most powerful contractor's desire action drama begins!