A one-shot published in Jump GIGA by Hajime Koumoto under the name Koichirou.

This is a world of magic where magic is used for everything. But deep in the forest exists a young man who spends his time training and bulking up. He can't use magic, but he enjoys a peaceful life with his father. But one day, his life is put in danger! Will his muscular body protect him from the magic users who are out to get him? Powerfully trained muscles crush magic as this abnormal magical fantasy begins!
 
(Source: MANGA Plus)
 
Note: 
- Eleventh place of Tsugimanga 2020 Award in the Manga Category.

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