Mae Khun Aei

Grandma Pim lives with her orphaned granddaughter, Saraphi, and her young grandson, Jao Mai, in an old wooden house by the canal. Saraphi is a physical education graduate who excels in various sports and martial arts. She works part-time as a trainer at a sports center, where she meets Ek, a young boy who wants to learn how to swim but was sent to learn Taekwondo instead.
Next to Saraphi's home are two large houses within the same compound. One belongs to Kornkanok, who despises Saraphi for refusing to sell her land. Kornkanok constantly harasses Saraphi and her neighbors by blocking their entrance and throwing loud parties at night. Unable to take it anymore, Saraphi retaliates by throwing stink bombs, scattering the party guests. Kornkanok reports Saraphi to the police for harassment, but when Captain Wenai investigates, he realizes Kornkanok started it. Not only does Wenai drop the charges, but he is also highly impressed by Saraphi. He speaks admiringly of her to his friend Fuengfa, unaware that Fuengfa is Saraphi's best friend and secretly in love with him.
The other large house belongs to Thewan, the President of Siam Parade, an import-export forklift company. He took over the business after his older brother, Theptai, and his sister-in-law, Kornnik (Kornkanok’s sister), died in an accident. Since then, Thewan adopted their son, Ek. Because he works late into the night, Thewan is mostly unaware of what happens at home. Kornkanok is secretly in love with Thewan and tries to get close to him, but he ignores her because his heart still belongs to Wanthip, his former fiancé who drowned before they could marry. This tragedy caused Thewan to develop a severe fear of water, and he strictly forbids Ek from going near it.
While looking for a full-time job, Saraphi sees a hiring notice for an agile secretary at Siam Parade. Thewan initially rejects her, doubting a woman's capability for the demanding role. They argue, with Saraphi defending women's equality and Thewan dismissing her views as idealistic. Determined to prove him wrong, Saraphi insists on taking his test. During a company event, Thewan encounters Chitphong, a former employee he fired for embezzlement, who now runs a rival business. Seeking revenge, Chitphong sends hitmen after Thewan. Thanks to Saraphi's quick thinking and combat skills, Thewan survives. Impressed, he officially hires her, which sparks intense jealousy in Saengjan, the company's other secretary, and Kornkanok. Both women constantly try to sabotage Saraphi, but she always outsmarts them.
One day, Ek sneaks out to play in the water and nearly drowns. Saraphi rescues him and subsequently agrees to secretly teach him how to swim. Meanwhile, at work, Saengjan locks Saraphi in the office late at night. That same night, Chitphong sends men to steal company documents, but Saraphi beats them up and calls the police. Thewan arrives and offers to drive her home, finally realizing she lives right next door to him.
Later, Captain Wenai brings Thewan to Saraphi's house to discuss the break-in, leading Thewan to discover that Saraphi is Ek's swimming teacher. They argue, but over time, their constant bickering turns into a close bond. Thewan is deeply impressed by Saraphi's competence and straightforwardness, while Saraphi begins to admire his dedication. Upon learning about his past trauma, Saraphi deliberately pushes Thewan into the water and jumps in to help him, eventually teaching him how to swim and overcome his fear. Grateful, Thewan finally allows Ek to learn swimming from her. Thewan even buys Saraphi a motorcycle for work, and they grow closer as he rides pillion with her during traffic jams.
Furious at their growing closeness, Kornkanok teams up with Chitphong to embezzle from Thewan. Thewan and Saraphi investigate and trace the stolen funds to Kornkanok and Chitphong. Thewan demands compensation, but Kornkanok denies everything, using her late sister's past contributions to the company as a shield. Thewan spares her but gives her a final warning. Panicked, Kornkanok consults Chitphong, who insists they must kill Thewan, which makes Kornkanok hesitate because she still loves him.
Hitmen attack Thewan and Saraphi again. Saraphi drives fiercely to escape, and Thewan takes a bullet to protect her. This makes Saraphi realize how much he means to her. Meanwhile, Kornkanok manipulates Ek against Saraphi. Seeing Kornkanok hugging Thewan at his house, Saraphi misunderstands and decides to step back, thinking they would make a complete family.
Captain Wenai confesses his love and proposes to Saraphi, breaking Fuengfa's heart. However, Saraphi turns him down, admitting she loves Thewan and only sees Wenai as a brother. She then resigns from Siam Parade. Thewan begs her to stay, hurt that she doesn't see their deep connection, but she leaves anyway.
A drunken and heartbroken Thewan tells Ek that no one, besides his family, loves him as much as Teacher Saraphi. Realizing the truth, Ek sneaks out to find her but overhears Kornkanok and Chitphong discussing how they brainwashed him. Ek angrily confronts them and is taken hostage by Chitphong.
Saraphi tracks them down to Chitphong's shipyard. Just as Chitphong is about to shoot Ek, Saraphi jumps in to shield the boy and falls into the river. Thewan dives in frantically to save her. Fortunately, the bullet only grazed her. On the way to the hospital, they finally confess their love for each other.
Thewan learns of Kornkanok's full involvement with Chitphong but chooses not to press charges for Ek's sake. A deeply ashamed Kornkanok apologizes for everything, and Thewan forgives her. In the end, Ek finally has a warm, complete family. Although Saraphi is technically his aunt-in-law, she loves him like her own son. Thewan learns to love again, knowing that while he will never forget his past, Saraphi is the woman he will love with his life. Saraphi is no longer alone in the world, having found both a loving partner and a perfect family.