In The Year 2056 in Xinghai City, a strange red aurora had appeared in the sky. The red aurora-attracted evil forces was released and turns into Monsters. In the heaven realm, a Wizard（仙翁）gives the fairy Meimei（美美）four different Crystal Bangles, told that she must find four talented people to transform them into Kaisers, a type of giant warriors to stop the monster.

Big Rally! Titan Boy! is the second movie of Choushinsei Flashman. It is a theatrical edit of episodes 15 to 18 (The Giant Robo is Worn Out, The Human Minimini Plan, The Mysterious Giant Reckless Car! and Big Turnaround! The Transforming Robo) with new and extended scenes.

French nuclear tests irradiate an iguana into a giant monster that viciously attacks freighter ships in the Pacific Ocean. A team of experts, including Niko Tatopoulos, conclude that the oversized reptile is the culprit. Before long, the giant lizard is loose in Manhattan as the US military races to destroy the monster before it reproduces and it's spawn takes over the world.

This roller-coaster ride includes kaiju, mad scientists, and humanoid robots, all seasoned with big, absurd humor and action-packed battle scenes.

Gaira, a humanoid sea beast spawned from the discarded cells of Frankenstein's monster, attacks the shores of Tokyo. While the Japanese military prepares to take action, Gaira's Gargantua brother, Sanda, descends from the mountains to defend his kin. A battle between good and evil ensues, leaving brothers divided and a city in ruins.

During WWII, Germans obtain the immortal heart of Frankenstein's monster and transport it to Japan to prevent it being seized by the Allies. Kept in a Hiroshima laboratory, it is seeming lost when the United States destroys the city with the atomic bomb. Years later a wild boy is discovered wandering the streets of the city alone, born of the immortal heart.

At the turn of the century, all of the Earth's monsters have been rounded up and kept safely on Monsterland. Chaos erupts when a race of she-aliens known as the Kilaaks unleash the monsters across the world.

Searching for his brother, Ryota stows away on a boat belonging to a criminal alongside two other teenagers. The group shipwrecks on Letchi island and discover the Infant Island natives have been enslaved by a terrorist organization controlling a crustacean monster. Finding a sleeping Godzilla, they decide to awaken him to defeat the terrorists and liberate the natives.

The Go-Busters must protect the Tokyo Enetower from the evil Vaglass organization. However Enter's new creation Steamloid causes the Buddy Roids to rust, making them unable to fight or be used in the Buster Machines.