Nekomaru and Inumaru are two minor characters from the Kishin Douji Zenki series. They wear worn out, traditional buddhist monk clothing, slippers and scarves with fluffy beads. They are bald and have golden eyes.
Nekomaru and Inumaru are brothers. The smaller one is Nekomaru, who is the younger brother, while accordingly the larger and bulkier one is his older brother Inumaru.
They first appear when they visit Shikigami-chou in search for Ozunu's secret treasure. The reader soon learns that the two brothers want to steal the treasure to sell it and become rich. Knowing that the treasure has to be located somewhere in the Enno Shrine, but not being clueless about the Enno Shrine's actual location, they soon wisen up when they overhear a dialogue between Chiaki and some other girls.
Nekomaru and Inumaru see their chance and already talk about how they will soon have so much gold that they will be rich till to the end of their lives.
When the two brothers follow Chiaki and her customers to the Enno Shrine, Nekomaru and Inumaru falsely assume that Saki Enno is dead. While the reader later on learns that Saki just left to return later on, it isn't obvious at this point.
When the sun sets, the two brothers decide to take action and break the seal of a box that is said to hold Ozunu's treasure. When the treasure turns out to be a Hyouinomi, it soon notices the brothers' desire and attacks them, turning them into a monstrous man with two heads, which soon becomes the two headed Hyouijuu Sairousaiko.
Another major difference is that Nekomaru and Inumaru don't wish to become rich and they don't turn Shikigami-chou into gold. (Another Hyouijuu does that in Episode 4)
Zenki VS Nekomaru and Inumaru's monstrous form
Because of Nekomaru and Inumaru's wish to have so much gold that they will be rich till to the end of their lives, Sairousaiko's special ability is to turn anything it touches into solid gold.
While the fight between the mighty Demon God Zenki and Sairousaiko starts almost immediately in the manga, the anime has Zenki start out in his Chibi form. Obviously the monster isn't too impressed by a small Chibi Zenki and immediately calls him a little twerp.
Anyways, even Zenki isn't exempt from the monster's ability and any part of his body that comes in contact with the monster also turns into gold. Despite this disadvantage, Zenki still easily defeats Nekomaru and Inumaru's monstrous form and eats the Hyouinomi, that is left behind.
Nekomaru and Inumaru are probably dead
The only tragic part of the whole ending of Chapter 1.1 is, that Nekomaru and Inumaru were probably completely consumed by the Hyouinomi and died, as they are never appear again. Despite them being two greedy men and thieves, one might still feel at least a bit like mourning over their loss.
As the brothers' names are Nekomaru and Inumaru, it is also possible to explain why they turned into a beast with a the head of a wolf and the head of a tiger.
As "Neko" means "cat" and "Inu" means "dog" in Japanese, it becomes very obvious which brother turned into which part of the Hyouijuu.
It can also be assumed that them being brothers, is the reason for them being merged into one beast instead of two.
While Nekomaru and Inumaru themselves only appear in the very first episode of the anime and the first volume of the manga, Sairousaiko also shows up for an introductionary boss-battle in Kishin Douji Zenki for the Sega Game Gear!
Anime (Episode 1)
Manga (Volume 1)
More images will be added soon.