Mikhail Cronin serves as the chief engineer at the Tamakoma Branch. He presents with long dark blond hair tied in a ponytail and favors a long coat and scarf in daily life, switching to a black jacket for work. Cronin maintains a collected, serious demeanor and consistently shows respect toward Tamakoma members through formal honorifics. Beyond his engineering duties, he unwinds by playing video games online with colleagues like Yuu Kunichika and Itsuki Fujisawa, exhibiting workaholic tendencies.

His background includes an association with Border during its initial public phase, though evidence suggests he joined after its earliest group photograph. Possession of a Kogetsu trigger during Border's formative period implies a past combatant role. His disclosed Canadian nationality and the potential alias "Michael Cronin" serve as covers for his unspecified Neighbor origins.

Throughout Border's operations, Cronin provides background advisory support. During the Black Trigger Capture Arc, his input surfaces in discussions about Yūma Kuga's enlistment. He briefly appears in the Large-Scale Invasion Arc for technical analyses of Tamakoma's triggers. In the B-Rank Wars Arc, Jin consults him regarding Hyuse's recruitment, and he is later observed approaching Tamakoma's base alongside Yuri Rindō. His involvement consistently aligns with strategic or logistical support for Tamakoma's initiatives.