Kamen Rider Chronos seems not to side on both Ex-Aid Side or even the Bugster Side. His identity is not known but we came to know one thing that he is not going be Graphite or even Emu. This is because Chronos is seen attacking Graphite Bugster Level 99 and even attacking Kamen Rider Ex-Aid Maximum Gamer Level 99 (first pic's top right). He also has the ability to stop time.
Videos by Cast
Bamba Disguises Himself as Towa on Towa's Day (October 8th)
Uhr Says to Visit Kamen Rider Zi-O: Final Stage