Bundai  

Bundai is an aggressive language teacher who kidnaps and forces Mugen to learn reading and writing. He uses unorthodox methods such as punching the student when they make mistakes and intimidating them with an inferiority complex if they don't progress quickly enough. Despite this, his approach appears effective, as Mugen learned to read and write in just one day and even created the infinity symbol, which he claims represents his name. It is possible that Bundai's methods were a form of revenge against Mugen for not being able to pay him back after a drunken night out where Mugen was unable to read the menu.