Following the events of Part II, Itsuki and the gang's "Rave" business is close to getting off the ground. Itsuki looks to Meryl Hathaway, a young girl often seen accompanying Kotoko, as a counter to the violence of the Umon-kai as he searches for a way to destroy them once and for all.

Despite running into plenty of trouble along the way, Itsuki was able to escape his predicament with Kotoko Teshigawara's help.

The gang’s business is close to getting off the ground, and a plan to destroy the Umon-kai is steadily taking shape inside Itsuki's mind.

However, that plan is still far from guaranteed to work, and should the Umon-kai get serious, everything he has worked so hard to build will surely crumble in the face of overwhelming violence.

There's one more way to make certain—

Itsuki searches desperately for a counter to the threat he faces.

Eventually, despite knowing the risk, he approaches “Meryl Hathaway,” a young girl often seen accompanying Kotoko, and tries to make contact with the overseas syndicate she belongs to.

From amidst the trickery and scheming of both organizations, a glimmer of hope emerges.

Will Itsuki be able to seize that light?