The ass-blasting sensei is a Japanese man who taught Denzel to do ass-blasting in the same discipline of martial arts. He taught Denzel how to do ass-blasting for many years, but then Woody said ass-blasting isn't real. When the sensei told Denzel it was time for his next lesson, Denzel told his sensei there's no such thing as ass-blasting. The sensei immediately believed Denzel, angrily asking "Then what have I dedicated my whole life to?" and he ran away, then sound effects show that he piloted a plane screaming "BANZAI!!!!", committing suicide by kamikaze by flying himself in a plane into a mountain. In real life, the Japanese Air Force committed kamikaze to attack Allied forces, such as Americans, during World War 2.
However, later on, it turns out that ass-blasting is real and Denzel won a trophy from a competition for doing so.