Another morning in Cammy Isles, where Coyo the Chameleon and Igoo the Iguana are seen enjoying a feast in the jungle, where Igoo has visited. Suddenly the two are met with the remains of Lerna's ship, sailing onto the shores of Cammy Isles. They go to check it out, and are met with a worn out King Lerna and his sub-ordinate, Anton the Monkey. Lerna explains that the ruler of Tartaroon, the land of the dead, named Minos will bring war upon Asha, and turn it into his domain. After hearing this, Lerna tells that the 3 forgotten isles are the key to defeating him. Each island holds the ancient ruins - Appa Ruins, Ota Ruins, and Ambda Ruins, and that these hold the ancient Golden Melons. The Golden Melons can grant one wish if all collected, and they can wish Minos to be sealed back in Tartaroon.
After collecting all Golden Melons, the 4 go to the place where the closed gates to Tartaroon lie, however, Lerna and Anton quickly snatch the Golden Melons. Lerna reveals that Minos was never able to leave Tartaroon, and wishes for the gates of Tartaroon to be opened, so he can use Minos's power to rule over the planet Asha. Minos, and his "bird" Caligo, turn on Lerna, and Minos plans to destroy all living things of Asha. Minos ascends to the air to release a massive wave over Asha, and, realizing his mistake, Lerna says that energy still exists within the Golden Melons, and Coyo splits the power between the four to face off against Minos.
They beat Minos and seal him in Tartaroon. The 4 return the Golden Melons and go back to Cammy Isles, where their bravery is celebrated. Lerna and Anton return to Lernia, and Igoo goes back to Iggy Isles, ending the game on Coyo resting after a long day.
The Legend of Coyo IV keeps all old elements, including the Tropicannons, Power-Ups, Healing Items, and even the Igma State. Coyo keeps his old moveset, but unlike previous games, instead of simple recolors of Coyo, accompanying him are Igoo the Iguana, King Lerna Hydrius, and Anton the Monkey. Igoo plays similarly to Coyo in his physique, but carries a spear - which revolves his main style of attacking. One push will make him lash out with the spear to any enemies near him, but doing a side attack will cause him to throw the spear like a projectile - killing any enemy that is hit by it. Igoo is the fastest of the bunch, however at the cost of this, his attacks are weak.
Lerna moves slow and has the smallest jump of them all, making him very heavy - however, he makes up for this with having an Health Meter of 40, contrary to the other members' 30. He also attacks the hardest out of the bunch, and his attacks are as follows: one simple push will make Lerna stomp the ground, sending a short shockwave to any surrounding enemies. A side push will cause Lerna to dart forward as well.
Anton the monkey moves as slow as Coyo, but can jump tremendously high. He can also cling onto ledges, but has the weakest attacks out of the four. His normal attack consists of him doing a weak attack with a banana, while a side attack will cause him to roll into enemies, hurting them. Also, a new feature is introduced, which can be unlocked in secret Eyezer fights - Eyezer, a secret boss in some Legend of Coyo games, has a secret door in each "Forgotten Island" level. Going through this will transport you to a secret room, where an Eyezer fight will occur. You need to fight Eyezer's form before it to unlock the next one, and each Eyezer fight is more difficult from the first to last of the islands. Beating all the Eyezer forms, you will unlock the level Tartaroon - where you can explore the underlands of Tartaroon, followed by a rematch with Minos.
- Prince Kibble's Cruiser (Fought at Serengact Jungle)
- Appa Ack (Fought at Appa Isles / Appa Ruins) / Eyezer 1 (Secret Boss)
- Khucken (Fought at Mrafland)
- Ota Ohc (Fought at Ota Isles / Ota Ruins) / Eyezer 2 (Secret Boss)
- Porcman (Fought at Porc Ocean)
- Ambda Aeq (Fought at Ambda Isles / Ambda Ruins ) / Eyezer 3 (Secret Boss)
- Caligo (Fought at Burned Sky)
- Minos (Fought at Final Zone)
Blah blah blah good game blah blah STYX will release another game...