the-death-spot
Explanation
The Joke
The comic shows a ninja master addressing his students, fulfilling a promise to reveal "the death spot" -- a point on the body that, when struck, results in instant death. He points to a diagram of the human body and identifies the spot as being on the heart, specifically the "superior vena cava." He declares that striking it causes "instant death." But then a student points out: "By the time your finger gets your finger around here, the dude is already dead." The master backtracks: "Did I say death spot? I said there was a death spot," implying he was just pointing out that the heart is vital, not revealing any secret martial arts knowledge. When students demand a refund, he flees.
The joke is that the ninja master's supposedly secret and deadly martial arts knowledge is just basic human anatomy -- of course destroying someone's heart will kill them. There is no mystical "death touch" or pressure point; he is just pointing at a vital organ. The humor of the students' objection is that reaching the superior vena cava would require essentially tearing through the chest, at which point the person would already be dead from the trauma.
The Humor
The comedy works by deflating the mystique of martial arts "death touch" legends. Pop culture is full of stories about secret pressure points that can kill with a single touch, but the comic reveals this "secret knowledge" to be trivially obvious -- hitting someone in the heart kills them. The master's hasty retreat and backpedaling when challenged adds a layer of con-artist humor, suggesting he has been scamming his students all along with repackaged common sense. The word "GAAAH!" as he presumably crashes through a window or runs away completes the farce.