Gender Swap: The Imperial Princess Becomes a King

(Reborn + gender swap + universe + war + empire + gender change)

A big truck turns into a robot, punches you in the head, and sends you to another world to become the protagonist. Would you go? Of course you would! Having a Transformer personally send you is so cool, isn't it? You're off to another world to be the protagonist! Which protagonist? The kind who rises to the top of life, marries a beautiful rich woman, and eventually retires and returns to Earth.