The third season of Koihime Musou. Han's high court general Kashin (何進) was forced to swallow a cursed pill from Chou Jou. The effect is slowly turning her into a cat, which she dislikes. Chou Jou also made use of the emperor's name to dispose her from the Han court as a traitor. She met Kada during her escape while Kada brought her to the Touka village, whom he believes they would help her.

College student Yuuhi Amamiya's monotonous life is turned upside down with the appearance of Sir Noi Crezant, a talking lizard claiming to be a knight of justice. Crezant elaborates that the world is in peril—threatened by the mage Animus who wishes to annihilate it with his Biscuit Hammer, an enormous structure suspended in Earth's orbit. As the newly appointed Lizard Knight, Yuuhi must fight alongside other Beast Knights to protect the princess and save the planet from destruction. Unimpressed by the prospect of risking his life, Yuuhi continues his day as usual—until a golem created by Animus suddenly confronts him. Yuuhi is instantly overpowered, but his neighbor, Princess Samidare Asahina, luckily rescues him. To his surprise, Samidare's intention starkly differs from Crezant's; instead of saving the world, she aims to destroy it with her own hands. Captivated by her firm ambition, Yuuhi resolves to become stronger and help Samidare realize her goal. As the pair continues to fight against Animus' golems, Yuuhi finds himself gradually gaining an interest in life—but the chains of his past trauma may restrain him from progressing further.

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.

Feelings may come and go, but true love always remains in the heart. Tsumiki Miniwa is in love with her best friend, Io Otonashi. For her, confessing is nearly impossible; but to her friends, they seem to be the perfect match. Cute and petite, Tsumiki comes off more as a friend, and Io's attitude toward her is friendlier than toward others. Despite the constant teasing and obvious hints that his friends have been dropping, Io always seems to miss the signs. Throughout her everyday school life, Tsumiki spends time with her friends and Io. Will she finally muster enough courage to confess her true feelings?