Hitori is actually the twins, Migi and Dali, who switch places and work together to seek the truth behind their mother’s death.
The story follows Migi and Dali, a pair of beautiful twin boys who lived in an orphanage.
Revenge is a dish best served by twins assuming a single identity, and said dish will most definitely be cold as ice in the Migi & Dali anime, which is on the way to adapt the seinen manga by Nami Sano.