This is a simple AU, more like a scenario but it follows the AU formula of changing it up.

Scenario A: (Enemy) is a cyborg. A robot that got sent back in time destroy (Crush). Of course though, as the only one to witness it and escape, it's your job to keep (Crush) safe, and prevent the end!

Scenario B: Scenario A but (Crush) and (OC)'s role are swapped.

Scenario C: You are a cyborg, sent back in time by the opposite group to protect (Crush). You need to get to them before the enemy group's cyborg catches them first!

Scenario D: Scenario C but (Crush) and (OC)'s roles are reversed.