A decade of peace is a luxury Kouji never earned, and the film knows it. The action sequences hit with the weight of someone who's already saved the world once and learned that victory doesn't mean you get to stop fighting. This is a franchise saying goodbye to its own legacy, not by destroying it, but by letting the person who carried it finally pass the weight to someone else.
A decade has passed since Kouji Kabuto piloted Mazinger Z to victory against Dr. Hell's tyranny. Now a scientist following in his family's footsteps, Kouji has left his hero days behind. Peace has settled over the world, fragile and assumed permanent. That changes when an inexplicable presence awakens beneath Mt. Fuji. An ancient structure emerges from the earth, bringing with it a mysterious lifeform that defies understanding. Whatever sleeps in those depths doesn't belong to any known science or history. Humanity faces a threat unlike anything before, one that forces Kouji to confront an impossible choice: ignore the danger and protect the normal life he's built, or answer the call one final time. The decision he makes could save civilization or damn it. Between the option of becoming savior or destroyer, Kouji must determine what kind of future humanity deserves. The past won't let him rest, and neither will what's coming.