Koshiro Sakaki is an instructor for the Machine Robo Rescue (MRR) organization, specifically leading and training the Blue Sirens rescue team. This team specializes in police emergencies, road accidents, and criminal apprehension. His primary duty involves ensuring the operational readiness and development of the Blue Sirens members: Robo Masters Makoto Aikawa, Susumu Utada, Tsuyoshi Utada, and Alice Beckham, providing guidance during both training and missions.

He typically maintains a composed and calm demeanor. However, documented occasions show he can display frustration or concern when trainees face difficulties or danger during operations.

Within the MRR command structure, he works alongside fellow instructors Musashi Miyajima of the Red Wings and Marie Bitou of the Yellow Gears. The MRR organization was co-founded by Brad Bitou and Tohru Suidohbashi.