Two lovers from enemy clans are handed a scroll with ten names on it, and the only way to cross off a name is to kill the person wearing it. The show grinds through every single death with the weight it deserves, never rushing past the moment when a character realizes they have to murder someone they might have respected. By the end, the truce between Kouga and Iga doesn't just fall apart, it was always a lie, and Gennosuke and Oboro watch their people die for a war that was decided before they were even born.

The Kouga and Iga ninja clans fought each other for centuries until the warlord Ieyasu Tokugawa ordered a ceasefire. Years later, the heirs Gennosuke of Kouga and Oboro of Iga have fallen in love and hope their marriage will bring lasting peace. That hope collapses when Ieyasu's two grandsons each claim the right to succeed him. To settle the dispute, each clan must send its ten finest warriors into a deadly contest, with each side backing one claimant. Two scrolls list the fighters, and a name is struck out in blood only when that warrior dies. The winning clan earns the shogunate's favor for a thousand years. Gennosuke and Oboro end up on opposite sides, caught between their love and their duty to their people, and in the end it falls to them to decide what becomes of both clans. Basilisk is an action drama with a romance at its center, adapted from a novel by Fuutarou Yamada.