Remember what I said about Professor Kuromatsu having a bigger role later in the series? Turns out I was right as he is the head of this plan! Based on his first test subject, it seems that it involves the use of the Flea Mutant to inject some weird liquid on someone's body and it seems that it can increase their adrenaline. Since the first test subject failed, the evil professor decides to look for another subject. This time, his latest subject is Kotaro's friend, Hayami who happens to be a racer.
As expected, he overcome his trouble in the hairpin part of the race track and is gaining more fans as he continues to win every race he is in. Because of his success thanks to the monster steroids, just like every guy who is taking a certain addictive drug, he wants more of it and the evil Professor gives him a better drug, to be exact, a hormone that will further boost his speed in the race track. Instead of boosting his performance, it makes him worse as he becomes a coward in the race track after he is injected with the hormone. I didn't expect that he will have that kind of side effect, I was originally expecting that he will turn into a Mutant or something since hey, the next step after in taking monster steroids is to become a monster!
Luckily, he escaped and Kotaro sees him. Instead of fighting Hayami, now a full-fledged werewolf with some of his consciousness left intact, he tries to comfort his friend. Heck, during the scene when he tries to run on a cliff to commit suicide, Kotaro decides to save him! This is when the Flea Mutant comes in and injects him the same hormone that turned Hayami into a coward. To be honest, I didn't see the effect of the hormone in Kotaro's body since the effect lasted for at least 2-5 seconds before he remembers what happened to his stepfather in the first episode.