Yajin Niroku

Yajin Niroku is the Shadow counterpart of Kuroninja, similar to how Anti-Kuroninja represents the Antiverse, which is located in the Mirror World. He is one of the main villains of Kuroninja Gold and the one who broke Lord Nemesis out of Darkprism.

History
Yajin Niroku used to be a good guy who helped out those who were lost in the Shadow Realm due to how dark it is. But then one day, he saw a bright light. The light corrupted him and turned him evil, making him think that helping random strangers is boring.

This part is still unfinished

Trivia

 * His name in katakana is Kuroninja’s name in katakana backwards.
 * Yajin Niroku looks like AbareKiller. This could be a reference to how both of them want to play killing games, and both fight the protagonist.