Singha (Mario Maurer) receives a call from Jazz, a high school friend. Jazz sets up a high school reunion for their class. The entire bunch meets up, they have a conversation and turns into Singha's last year of high school memory. Where he met his first and only love, Mituna (Apinya Sakuljaroensuk).
At first day of their final year in high school, Singha was waiting for a bus and had seen a woman fell down. He helped the woman and gave her a marigold flower, then rode a bus to go to school. They had two new classmates, Lam and Mituna. Mituna was late from class but was excused. She sat beside Jazz and Kanda whom she became friends with.
At first, Singha and his pals mocked Mituna for being silent. He got friends with Lam who helped him survive under Kong who tried to kill him. Lam became close with Singha's group. Singha made fun of Mituna when they become dance partners. Until, Mituna fought back in the bus because they made fun of her for helping a mute woman.
From that time on, Singha had been stalking Mituna because he wanna know where she lived. He asked forgiveness to her but Mituna did not want to talk to him. Singha's group together with Jazz and Kanda asked Mituna's mom to have Mituna be part of their project. They went upcountry and helped educate kids by giving them handouts and others. In a bonfire that night, Singha opened up his feelings by telling his most and second most favorite flower whom he referred as Mituna.
Mituna's pal and Singha's group became close to each other and helped fix Mituna's house. The group goes out together in resort and the skate club. Until, Singha and Mituna had fallen in love with each other. Lam was killed by Kong that brings sorrow to the group. Singha gave Mituna a paper to sign for their friendship book. She went home and had known that they had to move upcountry. In the final exam day, Mituna lied to Singha by telling him that she had to go upcountry for few days. After taking the last exam, she left a note to Singha that they would talk on the result day.
Prior to the result day, Singha's father was transferred and they had to move. On the result day, Singha decided to wait for Mituna but went with his friends. He got drunk and had fallen asleep. He woke up and look for Mituna in school and in her house. He ended up in the park waiting for her. He was caught by the cops but was recognized as son of a sergeant.
After the reminiscence, his friends told him at the reunion that if Mituna wanted to see him, she had showed up. He had to go upcountry for his job and found Mituna's mother. Singha met Mituna who was sick with AIDS and they talked to each other the whole night. Early morning, Mituna dies listening to Singha. Her mother gives him Mituna's thing who she wanted to be given to Singha. Singha read her notes and found out the day she transferred in that school, she found Singha who is the most important person in her life. He found out that it was Mituna's mom whom he had helped that day. The marigold flower he gave to Mituna's mom was kept by her and became the reason why she loved marigold. He found out that Mituna had kept her promise to talk to him at the exam result day To no avail. She ended up searching for him in his house only to find out that there was no one home. She then went to the park because it is their favorite place. She was afraid they will never say goodbye to each other, which was why she tried to go back to school. On her way back, she came across three men, the same three men who the cops were after in the middle of the rain. Even Mituna died but their love for each other will never end.