The war between the Terrans and the Vers Empire of Mars has ended, allowing humanity to blissfully enjoy their lives in a time of peace. Nineteen months later, however, the Vers princess makes a shocking public declaration: "the Terrans are a foolish race that covets resources, destroys nature, and are devoted to the pursuit of pleasure." And so, to protect their precious Earth, she calls upon her knights to take up arms, and the raging battle between the two civilizations reignites. Slaine Troyard has found a place among the Martians, giving Earth a short respite from the war against the Vers Empire. However, a peaceful resolution seems inconceivable. The various people who fought desperately for survival in the past now find themselves in the midst of yet another bloody and chaotic conflict, one that will forever alter the fate of humankind.

After finishing their "debut," Kate, Emilico and three other pairs who started with them begin a new life as adults.

The number of terrorist acts in Japan has never been lower, thanks to the efforts of a syndicate called Direct Attack (DA). The organization raises orphaned girls as killers to carry out assassinations under their "Lycoris" program. Takina Inoue is an exceptional Lycoris with a strong sense of purpose and a penchant for perfection. Unfortunately, a hostage situation tests her patience, and the resulting act of insubordination leads to her transfer out of DA. Not thrilled about losing the only place she belonged to, she reluctantly arrives at her new base of operations—LycoReco, a cafe in disguise. Takina's new partner, however, turns out to be quite different from what she imagined. Despite being the famed Lycoris prodigy, Chisato Nishikigi appears almost unconcerned with her duties. She drags Takina along on all kinds of odd jobs under the simple explanation of helping people in need. Takina is even more puzzled when Chisato takes down a group of armed assailants without killing any of them. Feeling like a fish out of water, Takina itches to get reinstated into DA—but Chisato is determined to prove to her that there is more to a life than just taking them.

Kou Yamori is an average middle school student who struggles with grasping the complex concept of love. Because he sees little sense in surrendering to the norm, he soon stops going to school. Plagued with insomnia due to his idleness, Kou begins roaming the lonesome streets at night. One night, Kou encounters a bizarre girl named Nazuna Nanakusa who believes that people stay awake during the night because they are dissatisfied with how they spent their day and cannot rest until they release their inhibitions. Nazuna offers to help Kou with his sleep issues and invites him over to her place, where she convinces him to share a futon with her. Feeling uncomfortable, Kou only pretends to doze off—which is when Nazuna suddenly bites his neck and reveals herself to be a vampire! While Kou thinks the bite will turn him into a vampire, the specifics of transforming are not that simple. In order to change, he must be bitten by someone he truly loves. Ready to let go of his dreary mortal life, Kou decides on a new goal: he will fall in love with Nazuna and become a vampire.