[The 48th Ronin]

Just a random idea:

The world was sent on the road to apocalypse when Aldnoah, a highly sentient AI, declared war on humanity. Using Kataphrakts, a type of virtually indestructible intelligent combat machines, wipes out more than 80% of humanity.

As the humans faced imminent annihilation, they decided on a last ditch effort for victory: Project Zero. By luck, they managed to capture a Kataphrakt intact and, using extracted information from it, created anti-Kataphrakt weapons. The Sleipnir series is the first of the new anti-Kataphrakt battle androids. It was never used in combat though, due to being immediately succeeded by the much improved Areion series.

With the new weapons, humanity managed to stave off defeat for a few more years. But they knew it won't last. They need to turn the tide. And that one fateful day, they find an answer.

From the ruins of Tokyo, the resistance found a fully functional time machine. With it the humans planned to win the war, by changing the flow of history. They sent a Sleipnir codenamed Orange back in time to prevent Aldnoah from existing by either killing its creators, Dr. Troyard and Dr. Rayregalia, or Troyard's son, Slaine, who somehow caused the AI to start the war.

As Orange, now goes by the name of Inaho Kaizuka, lands in the year 2014, he stumbled a girl named Asseylum, Slaine's soon-to-be wife via arranged marriage.