- Created by: Yoshio Sawai
- Voiced by: Taiki Matsuno (Japanese), Terrence Stone (English)
- Age: 42
- Date of birth:
- Occupation: Emperor (Maruhage Empire)
- Titles: Tsuru Tsurulina IV (Maruhage Empire)
- Hydrate (Younger Brother)
- Episode Appearances: 1-2 (shadow) 17 (cameo), 23, 26-27, 45-46, 51-55, 70-76
- Manga Chapters:
The leader of the Maruhage Empire (マルハゲ帝国, Literally translated as "Bald-Shaven Empire", though the anime changes this from the "Margarita Empire" similar to the drink Margarita). His Japanese name is a Japanese onomatopoeia for something slippery. Growing up, he was apparently wealthy, and at some point, he became the fourth leader of the Maruhage Empire. During his childhood, he was extremely cruel to his younger brother Hydrate, to the point where one day, without warning, Tsurulina had him thrown into the dark realm (an action that he would regret years from now).
Tsurulina's major accomplishment came in the form of conquering The Hair Kingdom (with some help from Bibibi-bi Bi-bibi), something that his ruthless predecessor failed to do! This however lead to the origin of his most hated adversary, Bobobo-bo Bo-bobo, who personally began to crush the emperor's forces as revenge for destroying his home!
The Fourth seems easily in control of his empire at the start of the series, but he slowly loses his authority as Bo-bobo and his allies take out his forces, from the Hair Hunters to his "Four Heavenly Kings" to even his prison island of Cyber City. Eventually, he further lost his grip as he was forced by Hair Hunters, cryogenically frozen one-hundred years ago, to release their leaders to take over this new era. As much as he hated doing this, the Fourth eventually decided this as the only way to keep his hold on power and defeat Bo-bobo. But when even this fell, the Fourth decided to enact his greatest plan: the "New Emperor Playoff", where all of the most powerful warriors of the empire were gathered together in a battle to determine the next emperor. His plan: To let all of his enemies take each other out, allowing for him to regain his grip on power. But what he doesn't expect is that his forgotten brother Hydrate had formed the Reverse Maruhage Empire, all for the purpose of taking over his tourney, using it to become emperor himself! The scared emperor bolts away knowing this, basically abdicating the throne and entering an early retirement alongside Mako-chan and Octopus Carl. Though he vows to rebuild his empire after it falls during Bo-bobo's battle with Hydrate, he does not accomplish this task, and Tsuru Tsurulina III builds a new empire after stealing the Hair Ball from Bibibi-bi Bi-bibi.
- Tsurulina IV also appears on the dollar bills of Halekulani.
- Tsurulina is married to a purple dragon-like thing named Mako-chan. Mako-chan can often be seen trying to suck out his brain with it tail (This doesn't even seem to be bothering Tsurulina at all)!
- Like Tsurulina III, he is a cyborg, but what he is capable of is unknown.