Kirino Kousaka embodies the ideal student with equally entrancing looks. Her grades are near perfect, and to cover her personal expenses, she works as a professional model alongside her best friend Ayase Aragaki, who abhors liars and all things otaku. But what Ayase doesn't know is that Kirino harbors a deep, entrenched secret that will soon be brought to light. At home one day, Kyousuke, Kirino's perfectly average brother, stumbles upon an erotic game that belongs to none other than his seemingly flawless little sister. With her reputation at stake, Kirino places a gag order on her sibling while simultaneously introducing him to the world of eroge and anime. Through Kirino, Kyousuke encounters the gothic lolita Ruri Gokou and the bespectacled otaku Saori Makishima, thus jump-starting an entirely new lifestyle. But as he becomes more and more involved in his little sister's secret life, it becomes that much harder to keep under wraps.

Humanity was caught at a precipice a decade ago when the first gates—portals linked with other dimensions that harbor monsters immune to conventional weaponry—emerged around the world. Alongside the appearance of the gates, various humans were transformed into hunters and bestowed superhuman abilities. Responsible for entering the gates and clearing the dungeons within, many hunters chose to form guilds to secure their livelihoods. Sung Jin-Woo is an E-rank hunter dubbed as the weakest hunter of all mankind. While exploring a supposedly safe dungeon, he and his party encounter an unusual tunnel leading to a deeper area. Enticed by the prospect of treasure, the group presses forward, only to be confronted with horrors beyond their imagination. Miraculously, Jin-Woo survives the incident and soon finds that he now has access to an interface visible only to him. This mysterious system promises him the power he has long dreamed of—but everything comes at a price.

With his muscular build and tall stature, Takeo Gouda is no ordinary high school freshman. However, behind Takeo's intimidating appearance lies a pure heart of gold, and he is considered a hero by his male peers for his courage and chivalry. Unfortunately for Takeo, his appearance does not bode well for his love life. As if his looks were not already enough to scare the opposite sex away, Takeo's cool, handsome best friend and constant companion Makoto Sunakawa easily, and unintentionally, steals the hearts of the female students—including every girl Takeo has ever liked. One day, when Takeo saves cute Rinko Yamato from being molested, he falls in love with her instantly. Unfortunately, he suspects that she might be interested in Sunakawa. Despite his romantic feelings for Yamato continuing to bloom, Takeo decides to act as her cupid, even as he yearns for his own love story.