What's "an OB" in the Karate Shoukoushi Kohinata Minoru manga? I have started reading Karate Shoukoushi Kohinata Minoru manga, and there is this title &quot;OB&quot; for some kind of teacher or guardian, like I supposed to understand what it means.
Google Translate doesn't know it, googling &quot;karate ob&quot; goes to &quot;obi&quot;, and I can't find any translator's note.


Well... being an OB, I really didn't want to get involved in such trouble, but...
(bottom-left panel)
According to the Oct. 1965 issue of Black Belt magazine:


  Beginning of (the Second Sino-Japanese War) in 1940, about 30% of Japanese colleges and universities had campus karate clubs allied with one or another of four principal schools of karate, referred to as "ryu." In addition to the club on campus, each of these universities had what is referred to as an "O.B." karate club. "O.B." here stood for "Old Boys" and was made up by the particular school's alumni. 


These OB clubs typically served as advisors for the student clubs. So "OB" here most likely refers to alumni, a graduate or elder disciple and liaison of sorts of that particular school, some of whom might later become instructors.

It would make sense, judging by the notches on Tachiyama's belt that he's a senior amongst the Judo club.

Here are the original pages for reference: