He was an experienced archery teacher located in Kyoto. Koizumi rarely gave lessons to individuals. At one point, he instructed Sojiro Nishikado. He later taught Haruto Kaguragi, who was preparing for the "Manly Man Festival." Haruto was a complete amateur at the time.
Koizumi was a middle-aged man, who had short black hair. He had short, thin eyebrows that only partially framed his eyes.
Personality and traits
He was a skilled, yet patient, instructor. He rarely personally taught archery and his abilities were certainly way above someone of Haruto's skill level. Koizumi never became frustrated with inadequacies and continued offering him encouragements.