When Gasper and Issei first met, Issei thought that he was another girl and was shocked after learning that he was a cross-dressing boy. Issei often reprimanded him for being a shut-in, although Issei and Gasper quickly became great friends and Issei trains him as his junior. Issei's blood gives Gasper a boost in power, even allowing him more control over his Sacred Gear for a short time. When Issei died in Volume 11, he, unlike the other members in the Gremory team, became very enraged, and defeated Georg afterwards after revealing his raw power.