Neptune

King Neptune is the King of the Ryuugu Kingdom on Fishman Island. He has 4 children (Fukaboshi, Ryuuboshi, Manboshi, and the Mermaid Princess). He was so angered by Van Der Decken's pestering his daughter through letters, and ultimately marriage proposal, that he had his 3 sons form an army called the Neptune Army to capture Van Der Decken.

While he is the king of Fishman Island, he has had to rely on the protection of 2 of the Yonkou: Edward Newgate until he died and Charlotte Linlin afterwards. He didn't have to pay collateral to Whitebeard, but he does have to pay a monthly amount of sweet candy to Big Mam.