Lol Gaban coc is not what caused Imu to bleed. Much off gurad, hello luffy and other didn't bleed from Imu coc Blast but you are telling Gaban coc blast would.hurt Imu. It was his ax attack. Gaban throw another attack which it cut bench which Imu is holding weapon, and he has bloodly face with frustration face.
Imu simply cut his arm wtih his weapon.