Kunal is a charming chef living with his architect girlfriend Diya, a caring and supportive partner. They are college sweethearts in a long-term relationship and are tired of their relatives constantly asking when they are getting married. To escape such questions during the wedding season, they decide to take a vacation to Sicily, Italy. While having lunch at a café, they meet Diya’s university friend Ally, a carefree wanderlust girl who is living in Sicily as a dance instructor. She convinces them to be their guide in Sicily, and the three spend their time partying, dancing, and exploring the island together.
One night, while sipping wine on a balcony, Ally privately asks Diya why they haven't married yet. Diya says that although Kunal loves her, she is unsure whether he truly wants to marry her or if their relationship has become a habit. To gain clarity, she asks Ally to flirt with Kunal to test his feelings. Ally eventually agrees, but warns Diya that she does not handle rejection well and not to blame her if her ego gets involved in this. As planned, Diya creates opportunities for Ally and Kunal to spend time together, but Kunal does not respond to her advances.
Eventually, Ally starts falling for Kunal as the two spend more time together, sharing romantic moments and discussing about love and Kunal’s relationship with Diya, and how they no longer have as much fun as they used to. When Kunal asks Ally about her relationships and what she wants, she looks at him longingly and leads him by the hand to the bedroom. The next morning, Ally wakes up in her bed and calls Diya, asking her to come soon. Kunal brings her coffee and tells her to forget what happened the previous night, saying they are adults and such things happen. When Diya arrives, Ally tells her that nothing happened and that Kunal rejected her. Diya feels relieved and happy. Later, while attending a wedding celebration, she proposes to Kunal. He accepts, and as the couple embrace, Ally realizes that she has fallen in love with him. Soon afterward, Kunal and Diya bid farewell to Ally and return to India.
Months later, Ally surprises Kunal and Diya by arriving in India for their wedding celebrations. She takes over the bridesmaid duties and grows increasingly close to Kunal, which Diya notices. One night, while alone with Kunal, Ally teases him about always listening to Diya and her demands, suggesting that he is getting married only because Diya wants him to. She questions his commitment and he admits that he would not have proposed to Diya but they would still be together. Ally describes her own version of an ideal wedding, which Kunal prefers. Ally confesses that she loves him and that he is the person she has been waiting for. Kunal is dumbfounded by her confession and left speechless.
At Ally’s insistence, Kunal and Diya hold separate bachelor and bachelorette parties during which Ally discusses her feelings with Kunal and then takes Diya's phone at her party. Unable to reach Diya, a drunken Kunal is picked up by Ally instead. During the drive, Kunal rejects Ally’s suggestion that they would be better together. The next morning, Ally openly confesses her feelings and challenges Diya to win Kunal before the wedding. Determined, Ally continues to drive a wedge between the couple, causing them to grow distant and detached during the wedding festivities and rituals. Eventually, Diya tells Kunal that he does not have to marry her out of responsibility and that she's willing to accept if he has feelings for Ally, but he remains silent when she asks whether he does.
Matters come to a head when Ally’s parents unexpectedly arrive at the venue, leading to a private confrontation in which Ally lets it slip that she had tried to seduce Kunal in Sicily at Diya’s request. Deeply hurt on knowing this, Kunal storms out and drives away. When Diya and Ally catch up with him, initially angry at them, Kunal finally admits that he has feelings for Ally and believes they might have been together had they met earlier. But he chooses Diya and their relationship shaped by years of comfort, trust, support and shared history. He says he will not tell Diya about what happened that night with Ally, but promises to stay with her in every lifetime. She accepts and Kunal and Diya get married. During the wedding, Ally gives the couple her blessings and reminisces about her time with Kunal, revealing that Kunal had rejected her that night in Sicily and that nothing had happened between them.
In an early mid-credits scene, Ally teases Kunal that she has no problem marrying divorced men and that if their marriage does not work out, he need not worry. The three share a light-hearted banter before Ally leaves the newlyweds to their wedding night.
