Johan's height, weight and birthday have been confirmed in the GX manga.
Johan Andersen , is a transfer student hailing from North Academy who enters Duel Academy in the third year. Johan is Scandinavian in the Japanese version while he seems to be from the Southern United States in the English version. He is kind, thoughtful, and sometimes shy.
Excitable and energetic much like Juudai (similarities between him and Juudai are noted in both versions, from their personalities to their ability to see Duel Spirits), he serves as one of Juudai's allies. Although a close friend, his disappearance serves a catalyst for Juudai's descent into darkness as The Supreme King of the alternate dimension. Johan is later possessed by the spirit of Yubel, Juudai's favorite card in childhood, using him and his Gem Beasts as mediators to act through.