Densetsu no Yankee wa Elite Salaryman?!

Souta is about to graduate from high school, but is feeling a bit bitter that he has not become the ideal Yankee he envisioned. One day on his way home, he is confronted by a dorky businessman with a short haircut and glasses, with whom his fellow delinquents have gotten into a fight! To Souta's surprise, the businessman turned out to be Keigo Morohoshi, a legendary Yankee whom Souta had looked up to! From that day on, Souta started going to Morohoshi in his spare time in order to become his apprentice.

(Source: Cosmic Shuppan, translated)