This is Son Gohan in the uniform he would train in for a year. After his old clothes were destroyed during his Great Ape transformation, Piccolo gave him new clothes and a sword. However, instead of 亀 (Kame, means "Turtle") symbol that adorns his father's uniform, Piccolo brands him as his student, and thus puts his 魔 (Ma, means "Demon") symbol on Gohan's uniform to do so. At the time, Piccolo deemed that it would be feasible to turn Goku's own son against him in his own quest for world domination. However, first he needed to be trained, to help defeat the Saiya-jins that were comng in a little under a year, lest there be no world to rule over.