Kothi's spies soon tell him that the Pandiyan king along with a small troupe of private guards of Greeks and local warriors will visit a hill top shrine in few days.
On the fixed day, Kothi launches an ambush attack on Ranadheera Pandiyan and his small private guards as they were en route to visit a hilltop shrine along a mountain path.
However, as the battle prolonged, the Greeks realized that it would be challenging to maintain the Phalanx formation for an extended period of time against Kothi and his determined forces.
In a selfless act of sacrifice, some of the brave Greeks laid down their lives, allowing Ranadheera Pandiyan and his close commanders to escape behind them to a nearby hill, connected by a narrow walking bridge.
The scene was filled with intense action as Ranadheera Pandiyan and his loyal commanders made a daring escape, leaving behind a battlefield strewn with fallen warriors from both sides.
The bravery and strategic skills displayed by Ranadheera Pandiyan's personal Greek and Local guards in protecting their king against overwhelming odds left a lasting impression on all who witnessed the fierce battle.
Ranadheera Pandiyan agrees and marries a young maiden from the "Perumpalli" tribe and impregnates her on their nuptial night, telling her that this consummation is merely for politics of men and not out of love for her.
As the marriage is consummated, the Perumpalli clan's matriarch leader gathers her tribe members, forms a large army, marches with the Pandiyan king to the Chola fort and lays siege to the fortress.
The sight of the multitude of Peruvirarkilli's army camped outside at the walls of the hill fort of Cholas makes some of Kothi's men mutiny against him.
Kothi's trusted and experienced commanders tell him that it is impossible and pointless to face the colossal army of Perumpolli's clan led by the furious Ranadheera Pandiyan and that they wouldn't stand a chance when they attack the fort.
The purpose of the contest of the two men meant that one who died or surrendered would have his kingdom handed over to the winner without a war, and the fallen man, if dead, had the right to have a funeral with full honours.
Kothi's wife, who was pregnant at the time of his demise, gave birth to a male child, carrying on the legacy of his brave father.
Meanwhile, the Chera warriors, who had been exiled to Arabia as slaves, returned to Tamil Nadu on Arab ships, ready to reclaim their lost glory.
The movie ended with the poignant quote, "A brave man stood against authority," encapsulating the legacy of Kothi's unwavering fortitude and defiance against all odds.
The story appears to be influenced by historical and epic fiction elements, drawing on the setting of ancient Tamil Nadu and featuring kings, tribes, and battles.
The themes that are prominent in the story include: bravery and defiance against authority, honour and sacrifice, consequences of actions, political intrigue and power struggle and cultural and tribal influences.
[7] Bhuvanesh Chandar of The Hindu wrote a review stating, "A few narrative stumbles aside, ‘Yaathisai’ is a truly commendable feat that one can look back on for its many positives.
"[10] Navein Darshan of The New Indian Express wrote a review stating, "Unlike the traditional war films where the focus largely lingers on the leads, Yaathisai gives prominence to the extras too.