Wataru Minakami is a top student who failed his high school entrance exam because of a computer glitch. He later discovered that he was accepted to Stargazer Hill Academy, which is located at a mysterious place called Promised Island. At the request of his father, Wataru is whisked away to the island, and before he can settle in, a dozen of cute and charming girls start to flock him and claim to be his younger sisters. As Wataru gets closer to his newfound siblings, a deeper mystery as to why they were sent to the island comes to play. (Source: ANN)

Driven to the verge of extinction by "Aragami," a race of all-devouring monsters, humanity makes its last stand in isolated points of resistance. Invulnerable to conventional damage, only "Oracle Cell" weapons—composed of the same matter which makes up Aragami—can kill these creatures. However, due to their god-like ability to adapt, the Aragami soon develop further immunity. Having no other hope of fending off the enemy, the remnants of human governments decide to detonate a nuclear reactor and wipe out the monsters facing Eurasia. The soldiers tasked with this mission are aided by three "God Eaters" dispatched from the Fenrir Far East Branch, an organization controlling what remains of Japan. The state-of-the-art weapons they wield, called God Arcs, are supposedly capable of piercing through Aragami skin and tearing their cores out, pulverizing the monsters. These mighty warriors may just be humanity's last hope of fending off the Aragami threat and averting total extinction. [Written by MAL Rewrite]

Thirteen-year-old Yasaka is a boy staying at his grandfather's house during his summer vacation. One day he entered a store and met Arashi, a beautiful sixteen-year-old girl working there. After trying to protect her from a man who claims to have been hired by her family to take her back by force, Yasaka ran away with her and now she stays at his grandpa's place with him. It didn't take much time for Yasaka to figure out that his new friend is far from an ordinary girl, as she possesses mysterious powers. The plot thickens when he finds a sixty-year-old picture of Arashi and another girl named Kaja, and to the surprise of all Kaja suddenly appears, and just like Arashi, her appearance hasn't changed at all since then. (Source: Wikipedia)

Hatsuki is a highschool student living with her sister, Hatsumi, who she has a huge crush on. On Hatsumi's 16th birthday, she is suddenly surrounded by a green light and disappears in front of Hatsuki. She manages to follow Hatsumi with the help of a being resembling a fat baby chick (literally), ending up in a place called "The Great Library", which is full of different worlds stored in books. Hatsumi wasn't there, though, so the search for Hatsuki's great love begins and involves traveling from book to book. (Source: AniDB)