The story begins with Qi Yue planning to confess her liking to the basketball team captain, Yuan Yi. She wrote a love letter and plans to pass it to him. Being as careless as only she can be, she has made her confession to the wrong person, who happened to be the school's devil, Ah Meng (her junior, a first year student in school). She is so shocked and embarrassed to see Ah Meng's face that she drops her love letter in front of Ah Meng and runs away. Ah Meng picks up the letter.
Ah Meng is amused by the whole thing and decides to have some fun with Qi Yue. He threatens Qi Yue to print a thousand copies of her love letter and let the whole school know of her liking for Yuan Yi. In order to stop Ah Meng, Qi Yue agrees to be his 'runner'.
With Ah Meng's continuous bullying of Qi Yue, she is driven to stop all the nonsense by confessing her liking to Yuan Yi again. In this way, she will not be afraid of Ah Meng's disclosing the love letter anymore. To Qi Yue's surprise, Yuan Yi has a similar liking for her.
While Qi Yue assumes that the whole ordeal with the devil is going to end, she receives another piece of bad news - her mom is going to marry the school's chairman who is also Ah Meng's father, which means Ah Meng is going to be her stepbrother.
Qi Yue's love letter is being put up on the school notice board and she misunderstands that it is Ah Meng who did it. She confronts him and storms off. After realizing that she has misunderstood Ah Meng, she apologises to Ah Meng and pleads him to hit her so that she feels better - Ah Meng kisses her instead. Yuan Yi happens to see them kissing and confronts their relationship, Ah Meng yells at Yuan Yi, saying that he wants Qi Yue. After Yuan Yi runs away in anger, Qi Yue looks at Ah Meng and begins to sob. After Qi Yue walks away in tears, Ah Meng has a strong feeling of guilt.
Yuan Yi regrets not believing in Qi Yue and returns to her, asking her out on a date. Qi Yue agrees happily. On their first date, they met Ah Meng again. Qi Yue and Ah Meng have some misunderstandings and they went separate ways.
After the date, Qi Yue left for home. After she took her bath, she fainted and was saved by Ah Meng's father. He brings her to his house to take care of her while her mom was away on a trip. Ah Meng and Qi Yue meet again at his house. She knows from Yuan Yi that she has misunderstood Ah Meng again. Seeing Ah Meng has injured his hand, she offers to clean the wounds for him. Sitting on Ah Meng's bed and putting medicine on his hand, she realizes Ah Meng is staring at her intensely and this makes her heart pound. Qi Yue wakes up and finds herself sleeping on Ah Meng's bed. Apparently, both have fallen asleep and Ah Meng's father has carried her to his bed.
Qi Yue finally realizes that the person she likes is Ah Meng. She tells Yuan Yi the truth and walks away. In the evening, she sits alone at the playground, crying softly to herself for hurting Yuan Yi. Ah Meng finds her and comforts her. She takes a ride on Ah Meng's bicycle. They had a minor accident and both fell on the road, unharmed. Qi Yue asks Ah Meng why is it always so dangerous to be with him. Ah Meng replies her that he cannot stop the dangers but he will protect her. Ah Meng kisses Qi Yue passionately on the road.
Due to their relationship as future stepsiblings, they keep their romantic relationship in the dark. Except for some close friends of Ah Meng & Qi Yue, nobody knows of their relationship.
Ah Meng's buddy, Yang Ping, who is in love with Li Xiang, is unhappy to see Ah Meng and Qi Yue together. He wants to get rid of Qi Yue so that Ah Meng can be with Li Xiang. At the school's rooftop, he ambushes Qi Yue and wants to kill her. Li Xiang hesitantly tells Ah Meng of Yang Ping's plan and Ah Meng rushes to Qi Yue's rescue. He beats up Yang Ping and brings Qi Yue home. At home, Qi Yue confesses her liking to Ah Meng and he hugs her, saying that he is happy to know that she likes him.
One fine day, a sweet-looking boy comes to Qi Yue and confesses his liking for her. This shocks Qi Yue and her whole class as he storms into her class and tells her that he likes her and wants her to convey a message to her boyfriend that he wants Qi Yue for himself. His name is Ah Rang.
Yuan Yi casually mentions this to Ah Meng and he storms away in anger. In the evening, he tells Qi Yue that nobody is more confident than him in liking her and she belongs to him only. Qi Yue smiles at his possessiveness.
Ah Meng's grandmother suspects that Ah Meng and Qi Yue are seeing each other. She plans to matchmake Ah Meng with a rich girl, Mei Di, which Qi Yue feels sad and uncertain. At the same time, Qi Yue's first love reappears as her school lecturer (Ah Sen). This causes Ah Meng to be jealous and he feels insecure. Ah Meng rejects Mei Di and she left wishing Qi Yue and him happiness. Similarly, Qi Yue tells Ah Sen that she likes Ah Meng and he goes back to his girlfriend.
Following that adventure, Ah Meng and Qi Yue take advantage of their parents' out of town trip to travel to see Qi Yue's father's grave. They get caught in a rain storm and discover that the train is not running. Ah Meng gets a hotel room, but Qi Yue can't stand the tension and makes the trip back home to find her mother waiting for her. She finally confesses that she and Ah Meng are a couple. Since this is going to be a problem for the family, her mother decides that they will have to move out of the house. However, when she faints, they find out that she's pregnant. Though it isn't proper, they decide that they will support Ah Meng and Qi Yue's relationship, and continue their own.
While things seem to be going fine again, Ah Meng's mom comes back and wants Ah Meng to go to Italy with her to pursue his studies. When Ah Meng finally agrees to go with her, Qi Yue is heartbroken. At the playground, Ah Meng tells Qi Yue that she can continue to date other people while he is away but he will always like her only. They embrace. Together, they decided it was time to have their "first time" together. They attend their parents' wedding a few days afterwards.
Later that year, at Christmas time, Qi Yue goes out to get a part for the Christmas Tree that Ah Meng gave her the previous year. While she's out, she's grabbed off the street and blindfolded, thrown in the trunk of a car and taken to another location. It's a prank, orchestrated by Ah Meng's friends. When she takes off her blindfold, Ah Meng is standing in front of her. He tells Qi Yue that he's back and they kiss.