Why does the principal laugh when a guy is introducing himself?


In Sakigake!! Otokojuku, Heihachi Edajima picks up the phone and introduces
himself. As the other guy begins to introduce himself as well, Heihachi
Edajima starts giggling, as shown in the following image:

[![Edajima Heihachi
Laughing](https://i.stack.imgur.com/WCITD.jpg)](https://i.stack.imgur.com/WCITD.jpg)

Is there any particular reason for why Heihachi Edajima starts laughing in
this precise moment?

