The Arrival of Daiku-Maryu!

S1 E1: Daiya Tsuwabuki is a boy in junior high who is known as the town liar. He claims that five years ago, he was saved by a large mechanical dragon when he and his father were attacked at sea by mechanical beasts. Even his mother and his only friend Naoto don’t believe his stories, but Daiya has physical proof of his experience, a mysterious device given to him by a young girl, a member of the mechanical dragon’s crew. Then one day, his town is attacked by two monsters, and the mechanical dragon, Daiku-Maryu, shows up. Daiya sees the girl who gave him the device years ago, and ends up in the dragon’s head, which transforms into super robot Gaiking, the Giant of Flame. Learning that he has control over the giant robot, he fights the enemy and drives them away from his town.