Kuro is a black crow with large eyes and a large beak.
Kuro is obedient, bold, and highly intelligent. During the bombing investigation, Kuro is able to follow Shirou's directions and quickly infiltrate the Medical Center without being seen, boldly making decisions and acting on the fly. Michiru eventually gets caught but Kuro doesn't and is able to complete the surveillance mission and relay the information back to Shirou. When Michiru and Kuro first meet, it boldly flies and collides into her, then calmly perches on her head.
During the events of World War II, Shirou rescued Kuro along with Barbara Rose from a research facility. Kuro has not aged ever since the incident. For Shirou, who has no friends or family, Kuro is the only partner who can forgive his heart and is a right-handed person. He will always follow and support Shirou's instructions.
Kuro aids Shirou in his investigative work and is adept at stealth surveillance operations. Kuro is also able to communicate with Shirou remotely though it hasn't been explained how they are able to do so.
Kuro is Shirou's faithful and loyal partner. He is being looked after by Shirou and tends to take action on his own when he sees his master is in need of help.
- Kuro is black in color and the Japanese name translates to black literally.