Hm..well, since he covers most of his face with a turtleneck-like thing, i guess you should use a pair of jogging pants, and sort of a thick turtleneck for the top(dont knoe if that made sense to you but yeah
). my brother is going to cosplay as iruka, so i think you should try that out to wear underneath the vest. if thats too hot for you, try to find a thinner type of fabric. hope that helped some!