Since the title provided is a bit of a descriptive sentence rather than the official Japanese title, you are likely looking for the manga known in Japan as (or simply "Kyou Senshi" ).
The story centers on , the youngest son of a prestigious but remote military family living on the frontier. Having spent his childhood on the battlefield, Albert is a formidable warrior. At the age of 14, he suddenly realizes he is a reincarnator from another world and that his current life mirrors a game he once played. However, there is a catch: Since the title provided is a bit of
Successful stories avoid these by giving the mob a genuine character arc—learning to accept their power, or realizing that even mobs have responsibilities. Since the title provided is a bit of