A.D. 2087 - the United Lunar Empire Giganos wages war on the Earth Federation Military to take control of the planet and establish a rebirth of the human race. During an invasion of a colony by Giganos' forces, three civilian men stumble upon a trio of top-secret Metal Armor units called Dragonars and pilot them to combat the enemy forces.

When the secret occult society, Shiromorishuua, sends a huge monster to attack Tokyo, ASY, a peace-keeping organization in Japan, retaliates with a Gousen (metal faery). ASY's Gousen annihilates the creature after driving it into open ocean. Although successful, a surprise attack follows. A girl, floating in midair and glowing with radiance, strikes with a beam of light. This girl is Rouran. She knows neither her identity, her origins, nor why whenever she senses the Gousen or Kyoushi (reanimated corpses) she transforms into an avenging angel. As Rouran worries about her mysterious existence, Tetsuya kindly watches over her in Tokyo Arcadia, a settlement of expatriates and dissidents. (Source: AniDB)

A mysterious string of disappearances on a certain train has caught the attention of the Demon Slayer Corps, and they have sent one of their best to exterminate what can only be a demon responsible. However, the plan to board the Mugen Train is delayed by a lesser demon who is terrorizing the mechanics and targeting a kind, elderly woman and her granddaughter. Kyoujurou Rengoku, the Flame Hashira, must eliminate the threat before boarding the train. Sent to assist the Hashira, Tanjirou Kamado, Inosuke Hashira, and Zenitsu Agatsuma enter the train prepared to fight. But their monstrous target already has a devious plan in store for them and the two hundred passengers: by delving deep into their consciousness, the demon intends to obliterate everyone in a stunning display of the power held by the Twelve Kizuki.

Zenitsu Agatsuma is determined to be the subject of adoration by receiving chocolates on Valentine’s Day—and this year, he is taking no chances. Enlisting the help of his friend Tanjirou Kamado, the two are prepared to learn from some of Kimetsu Academy's most popular figures. Together, they ask Kyoujurou Rengoku, the history teacher; Giyuu Tomioka, the PE teacher; and Tengen Uzui, the art teacher, about the secrets to their popularity. However, only time will tell if following their advice will bring the same success for Zenitsu.