Being Told "Do Your Best" for 15 Years, My Magical Power has Grown to 9999 "The Strongest"

Although Royle is blessed with a good physique, he was told that he had no talent for fighting, and was forced to work as a lonely gatekeeper for 15 years. While he is working, all he can do is fantasize about the adventure stories in which he is the main character, and his job as gatekeeper is replaced by an "automatic surveillance interception magic tool" and he is laid off. Loyle is at a loss, but on the way to another town, he meets the saint Diz. After meeting her, he discovers that the "strongest original magic" that he always used in his delusions can in fact be used in reality...