Michael Cronin/Plot

Background
He was seen with the initial members of Border when it first went public, but in the group picture in Kido's old room. This probably means he joined Border sometime after the picture and Border becoming public. He also had a Kogetsu, which could mean he used to be a combatant.

Black Trigger Capture Arc
He is mentioned by Kazama when he discusses about Yūma's enlistment in Tamakoma Branch.

Large-Scale Invasion Arc
He is briefly seen during Replica's explanation on Tamakoma's Trigger.

B-Rank Wars Arc
He is mentioned by Jin when he discusses about Hyuse's possible enlistment in Tamakoma Branch. He is later seen walking towards Tamakoma's base with Yuri.