Bundai

Bundai is an overly aggressive language teacher/tutor who kidnaps Mugen and force-teaches him to read and write. His methods appear extremely unorthodox, including punching the student in the face for mispronouncing words and intimidating them with an inferiority complex if they fail to learn literacy. However, one might observe that this extreme form of "teaching" was Bundai's way of getting revenge on Mugen for leaving him with the bar bill. The night before, Bundai had (drunkenly) harassed Mugen about his inability to read the menu, forcing him to drink a wine-like liquid while lecturing him on the "souls" of the letters.
His methods, however, seem to be very effective, as Mugen not only learned to read and write in a single day but (fictionally) created the infinity symbol, which he claims represents his name.