Thanks to the Mutant's influence, she starts to act like she is superior than other, especially to adults. Seeing her bully adults is one unsettling sight. I mean seriously, it doesn't look right, especially the part wherein she bullies the guy in the ice cream parlor to give them free ice cream. Thankfully, Kotaro arrives just in time to try and stop her. This is when the episode gets a bit more creepy, and in some parts, scary. The way they shot the scene where Kotaro is looking for the girl is really scary, it helps that music and the way the girl cries adds up the horror vibe of the scene.
Even if the Mutant now controls Mami's body, there are times that she fights back, and boy, she knows how to fight back. Heck, if I am interpreting the scene correctly, she used her super strength to open some wires so that she can electrocute herself so that she can release the Mutant! Now that the Mutant is now out of the girl's body, it is time for Kamen Rider to defeat him. The fight scene is as always, it's really good. One thing I can't help but notice is that this is longer than your average final fight scene in the series as the fight scene almost finished playing the full version of the opening theme.
At the end, the Mutant is defeated, the girl is safe and more importantly, Mami's father learn one important lesson about pressuring her girl to overexert herself in doing things.