Sigma Harmonics

The Kurokami family has been protecting the huge grandfather’s clock that prevents demons called Ouma from taking over the human world.
For centuries, this family has been doing their job in ascertaining that the human world stays untouched, however, someone has rewritten the past and humans are wiped out, completely replaced by Ouma.
It is up to Kurokami Sigma to right the wrongs that has been happening in history. Music, or tones are key weapons in the game as the Kurokami family controls sounds during battles.
Aside from battles, Sigma has to wrack his brains to solve the puzzles that leads to clues. However, the more mysteries he solves, the more people are killed, can he find the culprit before things become irreversible?