Gokakku

Gokkaku is the little brother of Rokkaku, and the true successor to Senkoukura.

About
Trying to prove himself worthy as the true successor, he steals Chibi and goes on a quest of bravery. However, he fails to even release Chibi's true form of Senkoukura. When Reiji comes to his rescue, Gokkaku finally recognizes him as the true master, no longer hindering him and later helping him.

Although he acts like a spoiled brat, he only wants to help everyone, but is constantly ignored because he doesn't truly own a dragon. In the epilogue, Gokkaku is seen riding on Thundervolt. While Rokkaku is seen riding on Mukai's dragon Shadow Fang, implying that Rokkaku gave Thudervolt to him while Rokkaku now owns Shadow Fang.