So this is the guy that beat the Demon King after plowing though the front line and storming the castle with a small party. Because the manga is so garbage at doing fights there is absolutly no way this guy is the one who won after barely managing to deal with a single demon with three days of planning.
He has the best armor money can buy, a super sword and can use magic. If his experience was what pushed him though this fight then what the hell has been all the other ones?