In Tamilnadu, Arjun grows up under the care of his Shankar and Priya, alongside his grandfather Shanmugam. Arjun has a soft spot for animals, especially dogs, and the story kicks off when the immensely successful breeder Fernando orders his henchmen to kill a newborn blind puppy from his kennel, intending to bury it on the outskirts of the city. The plan goes wrong when the pup escapes, and the henchmen lie about carrying out the deed, living in constant fear of Fernando discovering the truth.
Meanwhile, the family faces a mortgage crunch that puts pressure on Shankar, who is criticized by Shanmugam for prioritizing Arjun’s schooling over keeping up with payments. One day, Arjun stumbles upon the stray puppy and secretly bonds with it. The next morning, the pup uses its scent to reach Arjun’s bed, waking him up. Moved by pity, Arjun begs his mother to keep the dog, but she refuses. Undaunted, the puppy shows up again and soon becomes a fixture in Arjun’s life. Arjun, who names the puppy Simba, begins bringing Simba to school in secret, much to the delight of his classmates.
Fernando’s henchmen realize Simba’s presence and try everything they can to reclaim him, but their efforts fail. The school principal, with help from PT Master Swaminathan, uncovers the truth, and Shankar receives one last warning. After a heated confrontation, Shankar throws Simba out, and Arjun’s world derails as he falls ill from the loss. Priya persuades Shankar to take Simba back, arguing that Simba’s stay has helped Arjun behave and focus, and the family sets out to find the escaped pup.
The search leads them to a bear-blocked escape route, and a nightmare where Simba is eaten by the bear spooks Arjun into leaving the house alone at night. Eventually, Shankar and Priya find him with Simba, and the family officially welcomes Simba back. Shanmugam remains wary, but the bond strengthens. To help Arjun, the children at school begin raising funds for Simba’s surgery, learning about a two-lakh prize at the International Dog Competition in Coimbatore. With his father’s help, Arjun signs Simba up and earns a place in the finals, winning an early round and marching toward the title.
Simba is kidnapped by Fernando’s men but rescued by Arjun, who hides at a friend’s home. The henchmen are captured when Ladoo’s father, a police officer, intervenes, and they spend six months in custody. During that time, Simba continues to mature, and word spreads about a Russian doctor who can perform the required eye surgery for free. The doctor succeeds, and Simba regains sight just in time for the finals, heightening Fernando’s fear of the competition.
Back home, Fernando visits Shankar with an offer: he will pay off the mortgage if Simba can be bought. Shankar refuses, but Shanmugam’s anger flares. Financial misfortune hits hard, and Shankar fears losing the house. Seeking guidance, Shanmugam contemplates selling Simba, but fate intervenes when he suffers a heart attack that Simba narrowly helps avert by alerting the family. After recovery, Shanmugam agrees to help with the entry fee using his Old Age Security, allowing Simba to compete in the finals.
Fernando discovers Simba’s past blindness and deduces that the dog’s eye surgery could be jeopardized by flashing lights. In the finals, a policy blocks blind dogs from competing, but the crowd’s support and Arjun’s determination push Simba into the game. A pivotal moment arrives when Fernando tries to claim the medal by threatening Simba; Arjun intervenes, offers Fernando his dog, and pleads for Simba’s life as the host prepares to crown the winner. Realizing his mistake, Fernando exposes himself to the audience, relinquishing the medal and Simba back to Arjun, declaring Arjun the true winner.
Overjoyed, Shanmugam praises Shankar as the greatest father, and the family settles their mortgage and school fees. With Simba’s success and the financial burden lifted, the family finally enjoys a peaceful, hopeful future together.
