The film opens with a flashback, chronicling the childhood of Nandini and
Aditha Karikalan. Nandini was raised in a priestly family, and Aditha, training for his future as king, met Nandini during her visit to Pazhayarai. Love sparks at first sight for Aditha Karikalan, coinciding with Arulmozhi's horse race victory against Karikalan. Aditha's sister
Kundavai tries to befriend Nandini, but after discovering Nandini's orphan status, forbids her from palace visits. Nandini then deliberately ignores Aditha's attempts to reconnect. Then Aditha informs Nandini of his imminent military deployment. Saddened, Nandini prays daily by the river where he departed. Upon his return, Nandini confesses her love. Despite Kundavai's objections to Nandini's non-royal status, Aditha Karikalan and Nandini continued to love and see each other. Facing opposition, Karikalan introduces Nandini as the future queen. However, Kundavai and her grand-aunt
Sembiyan Mahadevi forcefully expel Nandini during Aditha Karikalan's absence, leading to his devastation upon learning of her departure and refuge under Veerapandiyan. In the current timeline, the presumed death of
Arulmozhi Varman, saddens the empire. Parthibendran Pallavan, smitten by Nandini's beauty, is manipulated into diverting Aditha Karikalan to Kadambur for the empire's well-being. Ravidasan and the Pandya Aabathudavigal ensure Ponniyin Selvan's demise.
Vallavaraiyan Vandiyadevan and
Poonguzhali, with a frail Ponniyin Selvan, encounter Azhwarkadiyan Nambi and Sendhan Amudhan. Vandiyadevan misleads Ravidasan and gets captured. Meanwhile,
Madhurantakan proclaims himself successor, aligning with Shivan Adiyars and Rashtrakuta King
Khottiga for vengeance. Nandini daydreams about Aditha seeing his Tiger Signet ring which he gave years ago. Later, she, Ravidasan, and others plot to assassinate Aditha Karikalan,
Sundara Chozhar, and Ponniyin Selvan. Nandini reveals her plan to kill Aditha Karikalan in Kadambur, overheard by the captive Vandiyadevan. He discloses seeing Oomai Rani, Nandini's mother-like figure, earning his reprieve. Disguised Nambi rescues Vandiyadevan, who informs Kundavai of Ponniyin Selvan's survival, reciprocating her feelings. Nambi alerts Aditha Karikalan of Ponniyin Selvan's existence. Kundavai and Aditha rush to Nagapattinam's Viharam, where Ponniyin Selvan is being treated. Aditha learns of Nandini's plot in Kadambur but dismisses Vandiyadevan's warning. Ponniyin Selvan reveals Oomai Rani's resemblance to Nandini, raising Kundavai's suspicions about her father's knowledge. She travels to Thanjavur, where Sundara Chozhar discloses his past with Mandakini (Oomai Rani's real name) in Lanka. Kundavai suspects Nandini's relation but learns Mandakini was pregnant two years after Sundara Chozhar's marriage to Vanavan Mahadevi. Pandyas plan to murder Ponniyin Selvan, but he foils their attempt. In Thanjavur's fort, Pandyas infiltrate, leading to conflict between Velar and Pazhuvettaraiyar. Madhurantakan flees through a tunnel to the Rashtrakutas. Ponniyin Selvan and Vaanathi arrive, bringing peace to the warring factions. Poonguzhali, spotting the Pandyas, alerts Chinna Pazhuvettaraiyar in Thanjavur. Meanwhile, Aditha Karikalan arrives in Kadambur. As Nandini and Aditha Karikalan lock eyes, Nandini reminisces the moments about her past, and how her love transformed into hatred. Periya Pazhuvettaraiyar and other kings propose dividing the kingdom with Madhurantakan, but Aditha Karikalan opposes, offering to relinquish the domain for Madhuranthakan's rule if he can keep his army for his siblings' safety. Everyone agrees to his condition. Periya Pazhuvettaraiyar heads to Thanjavur to inform Madhurantakan, but Karuthiruman, a rower who aided the Pandyas in Lanka, informs him of Nandini and the Pandya plot against Aditha Karikalan in Kadambur. In an attempt to rescue Aditha Karikalan, Karuthiruman hurries back to Kadambur, while the Pandyas use a tunnel to infiltrate the city. Vandiyadevan and Periya Pazhuvettaraiyar, also attempting a rescue, are knocked unconscious. Mandakini, attempting to reach Sundara Chozhar, takes an arrow intended for him and dies. Hearing his father's grief, Ponniyin Selvan arrives, defeats the Pandya assassins, and kills them. In Kadambur, Aditha Karikalan confronts Nandini, asking why she wants him there. As Nandini falters in her motivation, Aditha, who can read her mind, requests her to end his life, expressing the pain of being apart from her torturing him every day. Overwhelmed, Nandini cannot bring herself to stab him. Aditha Karikalan takes out his knife, hugs Nandini tightly, and pierces the knife into his heart, revealing his unconditional love for her. Nandini screams in pain, unable to see him die despite all the hatred she has developed for him through the years, revealing she still loves him. The Pandyas forcefully remove Nandini from Kadambur, saving her from execution. Meanwhile, Vandiyadevan and Periya Pazhuvettaraiyar, unconscious, are taken away by the Pandyas. Upon regaining consciousness, Vandiyadevan carries Aditha Karikalan's lifeless body to Parthibendra Pallavan and other kings, who accuse him of murder. Aditha Karikalan's maternal grandfather, Thirukovalur Malaiyaman, seizes Vandiyadevan and Sambuvarayar, the king of Kadambur, suspecting their involvement. Aditha Karikalan's corpse is taken to Thanjavur, where Sundara Chozhar, his family, and the public mourn his tragic demise. On a ship, the apprehended Karuthiruman reveals to a grieving Nandini that her father is Veerapandiyan, who raped Mandakini, leading to her birth, making Nandini an illegitimate princess. Nandini, feeling betrayed by everyone and traumatized by Aditha's death, drowns herself in the river Ponni, revealing her unconditional love for Aditha Karikalan. Nambi informs Chinna Pazhuvettaraiyar of Periya Pazhuvettaraiyar's location, leading to his release from the Pandya captivity. Vandiyadevan faces accusations in Sundara Chozhar's court, but Periya Pazhuvettaraiyar returns, disclosing the truth. Meanwhile, Parthibendran accuses Ponniyin Selvan of orchestrating Aditha Karikalan's death and allies with the Rashtrakutas and other rival kingdoms to invade the Chola empire for vengeance. Sundara Chozhar allows Vandiyadevan to assist Ponniyin Selvan in the impending battle. Madhurantakan refuses to fight against his homeland and sides with Ponniyin Selvan, contributing to the Cholas' victory. Later, Sundara Chozhar decides to abdicate the throne in favor of his only surviving son. However, on the coronation day, Ponniyin Selvan proposes crowning Madhurantakan, who adopts the name 'Uttama Chola.' The epilogue reveals that Vandiyadevan and Ponniyin Selvan led extensive conquests across the seas. After Uttama Chola's death, Ponniyin Selvan ascends to the throne as 'Rajaraja Chola,' while the Pandyas are captured and punished. == Cast ==