It's the last day of the school term in Kamakura Girl's School, and summer is about to begin. Serious but polite 14-year-old Ichika Tachibana is excited to make her summer vacation with her friends a special break to remember! But little does Ichika know that this summer will be more special than she could have ever imagined. While cleaning in an unused school building, Ichika notices an image of an unfamiliar girl in place of her own reflection in a large mirror. Convinced by her friends that she was just seeing things, she is surprised to see the girl in the mirror later that day, holding her lost cell phone. Introducing herself as Manatsu Kuroki, she comes out of the mirror and hands Ichika's phone back—and to Ichika's surprise, the stones on her cell phone charm have changed colors and now allow her to borrow the power of the 12 Djinn that watch over the world. Uta Kata is a tale of a young girl who will realize new things through her interactions with these spirits. As the Djinn show her overwhelming sights, they will soon also bring to her overwhelming thoughts...

In its expansion west to gain resources, the Europan Imperial Alliance invades the neutral Principality of Gallia, seeking to take control of its vast Ragnite deposits. Their strategic advantage, technological superiority, and military might make opposition nonexistent, so they steamroll through the border of the sleepy principality with ease. As Imperial forces run through his quiet hometown, Welkin Gunther and his younger sister Isara jump into action, banding with the leader of the local militia to push the occupational forces out of the village. Quickly retreating to the Gallian capital, they are organized into a unit with the remnants of the militia, tasked with assisting in repelling the Imperial presence from the country. Though unfamiliar with war, the newly formed Squad Seven must defend their country from annexation. But as the battle rages on through the streets of Gallia, ancient secrets will bring the team closer than they'd ever anticipated.

Naïve 16-year-old Mamori Tokonome is accustomed to being teased at school for having an unfortunate surname that can also be read as virgin. However, young Mamori will soon have to get used to being teased in other ways... Kidnapped during gym class, Mamori wakes up only to find herself stranded and under attack on the exotic island of Mermaid. Luckily, enigmatic fellow castaway Mirei Shikishima knows exactly how to take the lead—through a passionate kiss, Mirei unleashes Mamori's Exter transformation abilities, turning the innocent red-head into a battle-ready cutlass through the power of arousal. The duo will need to tap into that power as Mermaid Island is full of potential friends and foes: Charlotte, the sadistic Liberator of an Exter harem; the gluttonous and crafty Meifon; the mysterious but charismatic Akira Hiiragi; and the erotic biker duo Lady Lady. Mamori and Mirei's powerful and intimate embrace is the only way for the pair to ensure their survival on this scandalous island.

During the summer holidays, energetic Hana Uzaki spent most of her time accompanying her lonesome upperclassman, Shinichi Sakurai. Now that school has resumed, Uzaki's teasing continues to ramp up, much to Sakurai's constant annoyance. Nevertheless, no amount of ridicule can damage the pair's relationship—which only seems to be getting better as their college days fly by!