Hibiki is a very complex character, initially introduced as Kagura Mutsuki's right hand man (Who rarely puts up with any of Kagura's nonsense). Being raised in a family sworn to serve under the Mutsuki's, Hibiki hated Kagura at first, and stopped at nothing to one day assassinate him, something the Kohaku family line were masters at. Over the years, the two of them grew a mutual respect for each other, and have a complicated relationship that tips between the edge of platonic and romantic. It's hinted at during the new plot threads of Hibiki not being born male, but he has the respect of most of the cast that they treat him equally.

While he can be cold and uncaring during his time alone, he can have meaningful conversations with those he finds tollerable, and even share jokes.

Hibiki is voiced by Steve Staley in English, with an example being found here: https://youtu.be/3sukaZuPtmc?t=20

However, due to his implied past, this role is available to either actors or actresses alike.