1. Testosterone

It's the start of a new school year. Popular student Kwan becomes class president, while bad boy Win challenges the school rules in a big way.

3. Endorphin

Kwan and Win are both chosen to represent their grade in the Teacher's Day ceremony. Sprite's flirtatious ways get her in trouble.

4. Serotonin

Phai loses his friends when he starts dating Sprite. The girls at school gossip about Tar and Toei. Mhog keeps neglecting his girlfriend.

5. Estrogen

Toei walks into her classroom to find the word "slut" scrawled on her desk. Tar wants to reach out to her, but things are still awkward between them.

6. Dopamine

Everyone is gossiping about Toei's run-in with the older girls. Thee and Tar get jealous when Toei starts hanging out with her ex-boyfriend again.

7. Adrenaline

A monk tells Phai that he's heading for a fatal destiny, but he can't stop getting into fights. He's also increasingly jealous of his girlfriend.

8. Progesterone

Although worried at first, Dao's mother ends up being impressed with Din. So much so that she asks Dao to invite him over for dinner.

9. Cortisol

Through Win's manipulations, Kwan finds out that her father has a secret son. Sprite struggles with her "easy" reputation.

10. Testosterone & Estrogen

Kwan gets caught cheating on the chemistry exam, and the news spreads like wildfire -- along with rumors about her parents. Win feels responsible.

11. Oxytocin

Summer break begins. Win takes his frustrations out by sleeping with girls at the club. Kwan meets her father's family. Sprite's baby sister is born.

12. Growth Hormone

The students return to school. See Scape is performing at the Big Mountain music festival and Tar can't hide his excitement. Phu apologizes to Thee.

13. Hormones

The two-day Big Mountain festival begins. Everyone's there, including Dao, who's lied to her mother about where she's going.