Jill Savelle—fiancée of the crown prince Gerald de Kleitos and known as the "Lady Goddess of War"—is being hunted down by the same country she swore to protect. Betrayed by her betrothed, she is framed as a traitor and imprisoned. In her last moments, Jill is filled with regret, but just as death approaches, she awakens six years in the past. This time, she will not be a mere pawn. Now as a 10-year-old girl, Jill resolves to escape her imminent engagement to the prince. To this end, she jokingly professes her love to the 19-year-old dragon emperor Hades Theos Rave, who will one day stain the land in blood due to madness. But against all expectations, he accepts! In contrast to the tyrant from Jill's memories, the Hades of this time is a kind albeit unfortunate emperor. Can Jill prevent Hades from descending down the same dark, villainous road, or is he bound to an inevitable future?

Lamune tells the story of a boy named Kenji and his childhood friend Nanami. Although, everyone seems to know that they have a relationship, neither are determined to push it anymore than close friends. The story goes through flashbacks, explaining why they are such close friends and any action doesn't seem to push them apart, but draw them closer.

Himari Kino is a cheerful and outgoing girl who is able to make friends with anyone she wants. When she enrolls in high school and attends the freshman opening ceremony, Himari falls in love with Yori Asanagi, a reserved upperclassman, during Yori's band performance. After the show, Himari blurts out her love, but Yori is inexperienced when it comes to romance. Yori, who did not expect this outcome at all, looks for answers from her friends and music. She decides to respond to Himari's confession, and to her surprise, Yori discovers that Himari fell in love with her music and performance rather than Yori as a person. Despite the shock, Yori desires to make Himari truly fall in love with her. The duo spend time together after school on the rooftop, where Yori usually plays her guitar with hopes to change Himari's feelings for her.

Tomoya Mikami's life changed one day when his girlfriend Ayaka was hit by a car and killed on her way to meet Tomoya. He blamed himself for her death and never was the same after the accident. He began acting callously towards Yue and his other friends. Furthermore, every time Tomoya gets involved with a new girl, he sees images of Ayaka in his dreams. He decides he needs to find a way to say goodbye to his lost love once and for all, while dealing with several side romances at the same time.