In the aftermath of Amagami SS, high school student Junichi Tachibana continues his relationships with the girls at his school. Amagami SS+ Plus offers a glimpse into what happened after the resolution of each girl's individual story. New events begin to take place between each of the girls and Junichi. Tsukasa Ayatsuji, the class representative, runs for student council president; Rihoko Sakurai, who has taken over the Tea Club with Junichi, still wants to confess her feelings to him; Ai Nanasaki questions the future of her relationship with Junichi when he leaves for college; Kaoru Tanamachi wonders if her relationship with Junichi will ever go any further; Sae Nakata and Junichi deal with classmates who still can't believe that someone so cute is his girlfriend; and Haruka Morishima wants to take their relationship to the next level and get married. [Written by MAL Rewrite]

In the name of the king, the Valiante Kingdom launched hunts to exterminate users of witchcraft. Seventeen years later, their pursuit is still growing in both size and brutality. Unbeknownst to the citizens, the targets of these witch hunts are the secret protectors of humanity. Known as the Makai Knights and Alchemists, they have a strong will to protect people from Horrors, demons who possess souls plagued by sadness and pain. One such Makai Knight is 17-year-old Leon Luis who inherits the legendary armor of the Golden Knight Garo from his mother. Though he possesses great power, he struggles to overcome the hatred he bears from his mother's death at the hands of the kingdom. His father German, known as Zoro the Shadow Cutting Knight, is still training Leon when he is called to investigate the upsurge of Horrors in the kingdom's capital. Although German knows Leon's will is wavering, he decides to bring Leon along to continue his training. As German and Leon head to the capital, the king's amiable son Alfonso San Valiante struggles to find a solution to the growing Horror threat. But before he can do so, he is double-crossed and banished from his own kingdom. To return home, Alfonso sets out to find the help and strength he needs to reclaim the throne. During his search, he comes across Leon, whose interactions with the prince will forever change both of their fates. [Written by MAL Rewrite]

High school student Haru Yoshioka is bored with the monotony of life. One day, she saves Prince Lune of the Cat Kingdom from being run over by a truck. As a token of gratitude, the Cat King sends her "presents" and invites her to the Cat Kingdom to become Lune's wife. Haru's inability to properly communicate with the cats leads to the misunderstanding that she has accepted the proposal.

As Haru ponders on ways to escape the predicament, a mysterious voice instructs her to search for the Cat Bureau. However, not long after she finally arrives at the bureau, a horde of cats swarms in and forcibly takes her to the Cat Kingdom, along with a member of the Cat Bureau. Concerned for their safety, owner of the Cat Bureau, Baron Humbert von Gikkingen, follows close behind.

The more Haru immerses herself in the activities of the Cat Kingdom, the more cat-like she becomes. To her dismay, she soon learns that, unless she can find her true self, she may become a cat permanently. Haru's adventures in the world of cats lead her down a path to self-discovery, allowing her to return as a more confident person.

Succubi, like the young princess Astarotte "Lotte" Ygvar, require the life seed from men to survive, replenish their magic, and continue the royal lineage of the magical realm. This means succubi are required to keep a harem of men close at hand. Ironically, Lotte despises men, which will put her life at risk once she matures. To convince her to fulfill her duties, one of her attendants, Judith Snorrevik, goes to the human realm to find a human male whom Lotte can tolerate. Judith returns with 23-year-old Naoya Touhara, a single father who unfortunately leaves his daughter, Asuha, behind in the human realm. As the first member of Lotte's harem, Naoya quickly adapts to this new environment, serving the princess to make her happy, rather than viewing her with sexual intent. Unfortunately, when his daughter is allowed to arrive in the magical realm, Naoya's relationship quickly worsens with Lotte. Even so, he strives to patch up their relationship. It soon becomes clear, however, that Naoya's presence in the magical realm is more than just mere coincidence. As he develops his bond with Lotte, fate begins to pull together the connections that tie him and everyone else within this enchanting world. [Written by MAL Rewrite]