Kako, a clever and generous monkey, lives in a tall fig tree by the edge of the sea. Every day, he shares delicious figs with Big Fish, a shark who swims beneath the branches. Over time, the two become close friends, and Kako believes Big Fish can be trusted.

One day, Big Fish invites Kako to visit his underwater home, promising to carry him safely across the sea on his back. Curious and excited by the idea of seeing the wonders beneath the ocean, Kako agrees. But halfway across the water, Big Fish reveals a frightening secret: the king of the sea is sick, and the only cure is believed to be the heart of a monkey.

Kako realizes that his friend has tricked him, but instead of panicking, he uses his clever mind to save himself. He pretends that monkeys leave their hearts safely in trees when they travel. Big Fish believes him and quickly swims back to shore so Kako can collect his "heart." As soon as they reach the fig tree, Kako leaps back to safety and teaches Big Fish a lesson about betrayal and foolishness.