John Ayers Mackenzie is a longtime veteran of Gunpla Battle, going so far as to rival the second Meijin Kawaguchi.
In Gundam Build Fighters Amazing, he's a good friend of Takeshi Iori and was the one who convinced Tatsuya Yuuki's father to have Tatsuya enroll in Gunpla Academy. He also sent his grandson Julian Ayers Mackenzie to Gunpla Academy; believing that Julian is inexperienced about the darkside of Gunpla Battle, and only by learning about it could he truly enjoy Gunpla Battles. Unfortunately however, Julian's talent caught the attention of the 2nd Meijin Kawaguchi, who wanted to turn Julian's philosophy to that of utterly crushing the opponent. This ultimately led to Julian quitting Gunpla Battle altogether, much to the dismay of John Ayers Mackenzie.
Later on, John Ayers makes his reappearance at the 7th Gunpla Battle World Championship. He was the oldest competitor in the tournament, making it as far as the semi-finals, where he was slated to face the 3rd Meijin Kawaguchi. However, on the eve of his match he suffered an apparent heart attack. Hoping to inspire his grandson Julian to return to the world of Gunpla Battle, he pretended he was on his deathbed, and had Julian take his place in the tournament as a "dying" wish. He is seen reading a magazine while chatting with Mr. Ral, shortly after Julian's departure.