In the manga Osu!! Karatebu the word "osu" is used quite frequently, and from context I have so far assumed that it is a way for the junior members of the karate club to respond to their seniors in a general "yes, sir" way. However, I recently came across this panel which presents a quite different take on the word:
What is the significance of Shingo's particular dialogue about "osu?" Is it a typical philosophy of the character, karate, or a mix of the two? Why is it so different from how it is used elsewhere in the manga?