Kagaku Ninja-tai Gatchaman

Synopsis

In the Jupiter mountains, there are ruins of a fortress which is said to have been erected by ninjas of ancient times. Some strange corpses are found. Nambu charges Jun, who is familiar with this region, with the investigation.

Jun has found Jinpei in the Jupiter mountains. It was decided that this day would be Jinpei's birthday and it has been celebrated ever since. Despite that, Jinpei is in a bad mood that Jun has gone away this year because of the investigation. Ryu tells him that, since he doesn't know when his real birthday is, it doesn't matter when he celebrates it. Jinpei goes to the Jupiter mountains in order to research his real birthday and his origin.

Jinpei sleeps in the hut of an old man he met, but they are attacked by a Ninja group. Jinpei learns from the old man, that he used to be one of those ninjas as well and that, because he opposed Katse, his eyes were crushed while the chief and his family were killed. Only one person, the son of the chief, who was three-years-old at that time, was missing. However, the old man says that if he were to meet that child, he wished he could convey him the message that knowing about one's origin is not lucky. Then, he breathes for the last time.

Soon, Jinpei meets with Ken and the others, who have stolen the chariots of the ninja group and, led by the horses, hurried to the base together with Jun, who also sneaked into the base as well. They fight with the ninja group, who has been subdued by the Galactor army, and defeat the giant devil man, composed of the united ninjas, with the Tornado Fighter.

They couldn't learn Jinpei's origin or his true birthday. But as a reparation, Ryu hands Jinpei a birthday present. The present has been crushed in the fight, but Jinpei is nevertheless satisfied.

(Source: Wikipedia)