Hyper Hybrid Organisation

, also known as HHO or H2O, is a Japanese light novel series written by Kyoichiro Takahata, with illustrations by Yu Aikawa. The series began publication on November 10, 2005 by ASCII Media Works under their Dengeki Bunko publishing imprint.

Synopsis
The mysterious "black masked group" that made a noise in Japan was robbing, kidnapping, and sabotaging with a carefully planned strategy. A " remodeled human " whose whole body was covered with a hard outer shell played a major role in this, and its overwhelming power prevented the police from pursuing it. The only one who fights against the "black masked group" was the "Guardian," who also had a strange appearance.

Takahisa Yamaguchi was just a student and lived a life unrelated to the incident, but while meeting his girlfriend Yuriko Midorikawa, he was involved in a battle between a black masked group and a guardian. Then, Yuriko dies as a result of the attack that the Guardian made on the modified human.

Taking the opportunity of the incident, the black masked group announced the name of " Unicorn ". Yamaguchi begins to chase the unicorn and finally makes contact. Then he joins the Unicorn for the purpose of revenge on the Guardian.