Anon is examining the yukkuris' action of wiggling their bottom sometimes when they run... as well as how much it makes one want to crush them.
He comes up with the idea of suspending koyukkuris in wire netting, and does so with 5 of them, and films the anger-inducing scene as they wiggle and shake their butts. When he spots one starting to tire, he puts a lighter to its bottom (feet, mamumamu, or anyaru), and the koyukkuri will renew its shaking.
Eventually they get too tired to respond to stimuli, so he discards them and uploads the video on YuTube. The majority of the comments are nothing but 'I want to crush them'. The Professor with him tells him that he could make a lot of money off something so simple, but Anon says that he got carried away and tried doing it with 300... and he doesn't want to see any more for the time being.