Sleipnir

An experiment attempting to access the sixth dimension caused a massive explosion, killing 110 million and devastating 12 countries. Himeka Yuki, the experiment's creator, was exiled from reality for her role in the disaster. In response, world science leaders established the agency "Zeien" to regulate scientific research and prevent similar incidents. Ten years later, Takaomi Yuki, Himeka’s younger brother, discovers a change in the time machine his sister gave him before her exile. The device suddenly summons a girl in unfamiliar metal armor, who urges him to use a lance and ride with her to save Earth. Seeking answers, Takaomi and the girl embark on a journey through time and space.