Nai Ruen Jai

Korapin, or Pin (Piyathida Woramusik), is a quiet young woman who lost her mother at a young age. Due to the broken relationship of her father, Arjong (Athachai Anantamek), Pin has become introverted. However, her foster parents, Kritsana (Paothong Thongchua) and Khun Ying Angkana (Panarat Boonnark), manage to push her into social circles.
One day, she meets Kantayot, or Kan (Nawat Kulrattanarak). To the outside world, Kan appears to be a perfect gentleman, but he hides a dark past. During his studies abroad, he financially exploited and physically abused several former lovers—a reputation well-known to his close associates. Kan is encouraged by his mother, Khun Khemika (Suphansa Nuengphirom), to pursue Pin because of her family's status and wealth, despite the disapproval of his father, Kosol (Dilok Thongwattana).
Thanks to the close relationship between the two families, Kan easily gets close to Pin. Khun Ying Angkana, seeing Kan as a polite young man—unlike Theeradet (Atthawit Aphithanang), a politician’s son who is also pursuing Pin—decides to arrange a marriage between them. However, Arjong refuses to give his blessing. Knowing Kan’s notorious past, he blocks the wedding, forcing the families to settle for an engagement ceremony instead.
The lavish engagement party is the envy of many, but Kan is riddled with guilt and fear (the "cow with a scarred back"). His past comes back to haunt him when Komkrit, or Ko (Sam Showdet), a cousin who knows his secrets, appears at the event. Furthermore, Pin’s close friend Treethip, or Sam (Wayo Kiatkanok), also knows the truth about Kan’s history.
The story also follows a group of friends: Badisorn (Panyapol Dejsong) takes an interest in Nawapid, or Nong (Paradee Yoopasuk), and tries to recruit her as a model. However, Aradee (Passaree Kangwanpong), Pin’s bold and trendy friend, shamelessly offers herself instead. Badisorn, thinking Aradee is "easy," plans to just toy with her. Ruampol (Suriyont Arunwattanakul), Badisorn’s friend, is annoyed by Aradee and constantly picks fights with her.
Kan, fearing Ko will reveal his past to Pin, decides to tell her a "half-truth." Pin’s neutral reaction leaves Kan unsure of her feelings, but he intends to wait out the one-year period they agreed upon before marrying. Fearing Pin might give in, Arjong sends Ko to work closely with her. This infuriates Kan, who begins neglecting his work to keep an eye on her. Following Badisorn’s advice to give Pin some space, Kan ends up returning to his old gambling habits. Although Pin hears rumors, she dismisses them as harmless fun, yet the behavior of her friends and Ko keeps her suspicious.
During a company incentive trip abroad, Kan invites Pin, hoping for intimacy. However, the trip is crowded: Arjong forces Ko and Treethip to go along, while Badisorn and Ruampol join Kan, and Pin brings Aradee and Nawapid.
During the trip, Pin’s relationship with Ko improves. Initially rivals, she begins to see his dedication through their work, sparking deep feelings she tries to suppress for fear of repeating her mother’s tragic love story. Meanwhile, Kan runs into Jilla (Siriphan Hlimwijit), a woman he once swindled until she was nearly bankrupt. Fearing exposure, Kan tries to stay as close to Pin as possible.
Simultaneously, Ruampol accidentally insults Aradee, revealing the disparaging way Badisorn has been talking about her. A furious Aradee cuts ties with Badisorn, leading Ruampol to realize he had misjudged her character.
The climax occurs during a sightseeing trek when Pin slips and falls down a cliff. Ko is the first to rush to her rescue. In that moment, Pin realizes her true feelings and cries in his arms for the first time. Ko comforts her tenderly, though both are aware of the engagement standing between them. This intimate moment is photographed by Nawapid, who has unknowingly fallen in love with Kan. Her jealousy leads her to betray her friend by giving the photo to him.
Kan explodes in a fit of rage and physically assaults Pin in front of everyone. When Ko steps in to protect her, Kan’s frantic attempts to shift the blame onto Treethip end up exposing his own dark secrets. Finally knowing the truth, Pin no longer feels guilty about leaving the insincere man. However, true love always faces obstacles. How will their love story unfold amidst the confusion and the walls Pin has built around her heart for so long?