(Part of the potential-megaseries Ex-Hero And Demon Lord, Travelling Different Worlds Together, if I managed to even done this...) There used to be a pair of hero and demon lord, who faced each other in a climatic battle, to take back their happiness... Now that this is all done and all, they decided to fulffiled their childhood dream of travelling all around the worlds, and goes into another world for such reason. The first world they picked is filled with Mecha, as giant humanoid robot piloted by hotblooded man and woman duke against each other in constant battle.  ...Isn't that way too intense for a supposed vacation, the ex-hero think. And that's not mentioning further trouble brewed ahead...