From Baka-Tsuki:

The year was AD 2140. Under the menace of no mercy posed by "Aions", the worst enemies ever, mankind's population reduced to the extreme and was literally on the brink of extinction...

Encountering a strange incident, Nanagi Ryouga was sent flying from the peaceful world of 2015, and though shaken in that harsh environment, he stood up for the purpose of finding hope in his own fate and the future of mankind. Carrying a radiant sword in his hand— The curtains of the speed battle with a new perspective never seen before rises!