Average, everyday Japanese gameaholic gets sucked into an alternate world where he has summoner powers and life keeps turning out to be like one big video game.

From Seven Seas:
Three things you should know about Touga Eita, second-year high school student and heir to the Touga-style ninjutsu dojo: First, he really, really loves video games. Second, when given a choice between heroics and saving his own skin, he will always choose the latter. Third, he's never so much as kissed a girl.
All this changes when a voluptuous girl with wings and taloned feet named Aero appears and calls on Eita to help save her people-the harpies of Re-Verse-from the merciless onslaught of giant robot monsters known as Gigas. Eita will follow his newfound harpy friend into a whole new world, filled with monster girls and fantastical creatures beyond his wildest dreams.

From Seven Seas Entertainment:
Monsters? They're real, and they want to date us! Three years ago, the world learned that harpies, centaurs, catgirls, and all manners of fabulous creatures are not merely fiction; they are flesh and blood?not to mention scale, feather, horn, and fang. Thanks to the "Cultural Exchange Between Species Act," these once-mythical creatures have assimilated into society, or at least, they're trying.
When a hapless human teenager named Kimihito Kuruzu is inducted as a "volunteer" into the government exchange program, his world is turned upside down. A snake-like lamia named Miia comes to live with him, and it is Kuruzu's job to take care of her and make sure she integrates into his everyday life. Unfortunately for Kuruzu, Miia is undeniably sexy, and the law against interspecies breeding is very strict. Even worse, when a ravishing centaur girl and a flirtatious harpy move in, what's a full-blooded teenage human with raging hormones to do?