This episode was pretty much all about proving that Nikaidou is a bad guy. He sets his eyes on Kukai as the next person for his experiment, but his trap back fires. Nikaidou tries to make Kukai believe that Tadase is secretly looking down on him and that Amu favors Tadase’s opinion over his own.
The reason why Kukai’s input would be important to Amu is because Amu was chosen as the class representative for the speech contest. Tadase always makes good grades and is normally chosen to be the speaker in these contests, but Amu was chose due to her large fan base and partly because she was sleeping in class and couldn’t say anything against it. Her participation in this contest is the big incentive for Nikaidou’s trap, but when Kukai and Tadase noticed something was up, they decided to play along and catch Nikaidou red handed. Their plan works, they finally find out that Nikaidou is making the X eggs. Yea he gets away, but Amu wins the speech contest. Good episode!