Kiriko is the only connection Aries has to his childhood and the only person who can confidently say that Arielle is not Aries’ twin sister. Kiriko and Aries were born in the same research facility and played a role in the rebellion that led to Aries’ melding with the quantum fabric of existence. Kiriko was Aries’ best friend and primary sparing partner during their childhood. While Aries was created to become a vessel, Kiriko was created as a servant meant to be sold for profit before the rebellion of the facility.

During his adventures through dimensions, Aries found Kiriko working as a bodyguard for a corporate politician named Cidson Kuransagi, who took her in when he found her wounded and barely clinging to life after the explosion that sent Aries into his throne world. Cidson was kind to Kiriko, but her time in the facility had tainted her, allowing her to fit in with the darker sides of politics and business.

When Cidson died, Kiriko reached out to Aries for help to avenge him. The two of them tore through various criminal organizations as they unraveled the complex webs that led to her adoptive father’s death. By the end, Aries and Kiriko inherited ownership over the Nox Syndicate. This vast and powerful crime syndicate blossomed into a multi-dimensional organization under Aries’ leadership.

Kiriko is now the High Boss of the Nox Syndicate, traveling very often and managing a variety of corporations and criminal organizations that report to the Syndicate. While Kiriko moved on to marry Yuki Nox, she still deeply loves Aries and has become one of his consorts as an expression of her love and commitment to him.

Yuki, having no interest in owning her late father’s legacy, has given complete control of the Nox Syndicate to Kiriko and Aries and even moved into Aries’ castle to avoid being targeted by opposing organizations.