A passionate teacher, Kumiko Yamaguchi, a.k.a. Yankumi, is now overseeing the new students of Class 3D of Akado High School, who still have not opened up to her and are giving her a hard time. One day, the students of 3D get harassed by street hoodlums. Then, Reita, a leader figure of 3D, shows up and beats up the hoodlums, yelling "Keep your hands off my friends." The next day, the guys beat up by Reita come storming into their school. Principal Sawatari berates the students for getting mixed up with a gang, and gives Kumiko an ultimatum: "You're fired the next time a 3D student gets into trouble." Then Reita tells Kumiko that he doesn't want to owe her anything, and he takes off by himself to settle the score with the gang... Meanwhile, trouble was also brewing for the former 3D student who just graduated. The police are after Ren for being involved in an illegal drug transaction. Upset Kumiko tries to find him with the other former 3D students. However, they later find out from her grandfather, the head of the Oedo Family, the shocking identity of the mastermind pulling the strings of the drug deal Ren is being accused of...