Personalized Martial Arts Future Black Belt Karate Toddler Long Sleeve T-Shirt. Cute future black belt Toddler Long Sleeve Tee - Black for boys or girls interested in karate, martial arts sports. A classic for Fall, Winter and Spring, these long sleeve toddler t-shirts are sure to be a staple in your child's wardrobe. Whether layered or alone, this t-shirt is soft yet durable enough to stand up to your toddler's playtime demands.