Ziyoteru is the dark side and the 'evil brother' of Kiyoteru Hiyama. He is a science teacher who focuses mostly on spacial theory. When asked to describe himself, he simply says, "Science teacher by light, rockstar by night."
Ziyoteru (usually called Ziyo) differs from his lighter brother in appearance by three things; his hair, eyes, and tie. His eyes are crimson instead of black, and his hair is black but not brown. His tie is reddish-violet and not blue. His outfit is otherwise the same.
Ziyo is kuudere, meaning he is calm and collected, only showing his sweet side to very special people. He is known to have a lot of patience for his students, as they are known to disrupt his lessons. His patience is very limited around his light side, however. They often get into fights and although Ziyo refuses to show it, he has several scars because of it.
He is known to have a very sad past. If one stays around long enough to hear the full story, one will end up being tramautized, however the creator, Meiji, will give you the points.
First, he was created as a prototype. When the scientists were certain that they had everything correct, they left him to the streets, with no further use of him. One scientist, however, had enjoyed creating him and helped him a little bit in the early parts, by giving him some food and telling tales of his creation. Eventually, she was found out and was fired. She stopped visiting Ziyo and he figured that he wasn't needed and so, he left for the other side of Tokyo to start a new life.
After a decade of wandering, he found his brother Kiyoteru, who took him in. They lived together for roughly five years, before they were sent to a master in America. This master is unknown, but one knows that he was very abusive towards Ziyoteru and spoiled Kiyo rotten. He is known that he had beaten Ziyo more than once, however. He had favoured Kiyoteru, who had bathed in it and had emotionally tormented his older, darker brother. After seven years of this torture, Ziyo had enough of his torture and ran away. It was time that he moved out anyway, if he had been a normal human. Vocaloids were to stay with their masters forever, but he was not a true Vocaloid so it didn't matter. He ran west, across the continent to find a short, sweet girl who would become his master and finally, not abuse him. He remains there to this day.
- His favourite student is known to be Kurotane Piko, who he found not only is schizophrenic like him, but has also a very similar backstory. For this, they get along well and Kuro comes to Ziyo for advice on a lot of things.
- It is rumoured that he once had a major crush on Zaiko, a dark Meiko, but he never mentions her unless he has to.
- Ziyo enjoys spending time with his master, as he is grateful to her for not only taking him in but not abusing him.
- He rarely uses his character item, which is a Death Note.
- Although he is kuudere, when he shows his sweet side he can become very yandere extremely quickly. The only person who is capable of calming him down is his master, who simply talks to him in some sort of lullaby, which calms him back into his kuudere side.