Over a century ago, astral mages under persecution from the Empire banded together and established the Nebulis Sovereignty under three founding families: Lou, Hydra, and Zoa. With the leadership of Millavair Lou Nebulis VIII, the Sovereignty aims to minimize casualties in their conflict with the Empire—a stance the extremist Zoas disagree with. Tensions rise between the families as the upcoming election to decide the next leader approaches. The Zoas are willing to do anything to achieve success; however, a world-ending war may ensue should they be victorious. Princess Aliceliese "Alice" Lou Nebulis XI has no choice but to cooperate with any potential allies in order to advance towards her ultimate goal of ending the conflict that has long tormented everyone involved. This includes Iska—one of the Empire's greatest warriors and her greatest rival.

One day, high school student Michio Kaga attempts to start a strange online game he found while browsing the internet. Instead, he gets transported to a rural village in the game's world, equipped with special skills and an overpowered sword. After collecting his thoughts, he finds himself battling against bandits and soon realizes that he cannot log out. Resigning himself to fate and accepting this reality, Michio sets out on a journey—enjoying his new life, conquering dungeons to earn money, and building a harem to satisfy all his manly desires.

Poor Shinichirou Asano has the worst of luck. His parents abandoned him and ran off to Europe. If that isn't bad enough on its own, they barely left him any money to take care of himself. In order to pay rent and keep a roof over his head, he has to work. Unfortunately, he was just fired from his last job and as a high school student, he doesn't have many other prospects. One evening, he's attacked by a centipede monster on his way home. Shinichirou is saved by a mysterious girl with a bow and arrow, who he later discovers is Sakuya Shimazu, a beautiful student who attends his school. But when he later helps an injured girl, he discovers two things. First, the injured girl isn't human at all but rather a nekomata, a two-tailed demon cat. And second, Sakuya comes from a family of exorcists, who've protected humanity from rogue monsters and spirits for generations. Because Shinichirou was responsible for releasing the nekomata, Sakuya enlists his help in recapturing the demon, but that's just the beginning of Shinichirou's relationship with Sakuya. It turns out the Shimazu family needs a housekeeper and it just so happens that Shinichirou excels at cooking and likes to clean! It may not be his dream job, but if it pays the rent and puts food on the table...

Hida Kizuna possesses the HHG (Heart Hybrid Gear) ability, but it is not strong enough to make him particularly important. His older sister calls him to transfer to a strategic defense school, where many of the students (many of which are large-breasted girls) use their HHG abilities to fight invaders from another world while wearing extremely skimpy pilot outfits. Kizuna's fighting ability doesn't measure up, but his sister has another plan—apparently having erotic experiences with Kizuna will allow the girls to replenish their energy or power-up. It looks like his new school life is going to be full of embarrassment. (Source: MangaHelpers)