The Nekaiyo were introduced in Exenia's fourth expansion pack, Call of the Tides. According to Denny Shinohara (esteemed director of the Grand Drive series and guest writer for the CotT expansion), the aquatic Nekaiyo were introduced as the focus for this expansion as a result of his opinion that "underwater environments in full-immersion tech should be explored more thoroughly" and out of a desire to "bring more exotic mystery to the land of Exenia." He stated in the same interview that he also drew inspiration from his love for fishing, and "I just think cat people are cute." The Nekaiyo are native to the tropical archipelago of Lagarras and, possessing both gills and a set of mammalian lungs, have established a culture and lifestyle that takes place both below and above water - heavily revolving around fishing, underwater mining and shipping, able to swim, dive and sail to maneuver around the archipelago and move to and from the mainland. The Nekaiyo's main storyline revolves around hunting and killing the Wavebeasts that stalk and haunt the oceans where they live, with their very existence being threatened by the Wavebeast Prime whose size rivals the archipelago itself!
Unfortunately, the victory over the Wavebeast Prime is where the story of the Nekaiyo ends - poor reception of their story, concept, design and a perceived lack of interest in their underwater-based gameplay mechanics meant that the story and all content for the Nekaiyo was limited exclusively to CotT, with no further support offered after that point. :-( However, the Chinese Exenia servers received a great deal of additional content as a part of Exenia's extended support policy in those firewall zones! This expansion content greatly expands the underwater zone and adds a second set of islands far off the coast of Lagarras. This expansion greatly delves into the complexities of the Nekaiyo as a culture and their origins within Exenia, and how they connect to the story of Exenia itself! The already-rich and exquisitely detailed history and culture of the Nekaiyo, already unlike any other game's fictional race, becomes ten times as detailed and complex with this expansion... translations of the Chinese content can be found at the bottom of the page! :-)
Mechanically, the Nekaiyo are a mixed-specialization melee-based class with an emphasis on vertical movement, high DPS rates, and unique abilities that make high use of underwater environments for specialized positioning skills and unique magic traits. They have the unique, signature ability Swim, which (obviously :-]) allows them to move underwater not unlike the Skysinger's Fly skill, as opposed to simply sinking to the bottom and drowning like most classes... which Nekaiyo also cannot do, thanks to their gills allowing them to breathe underwater! Nekaiyo are also unique in their ability to equip multiple types of weapon; while the default is the Harpoon shared by Dragoons, they are also capable of equipping firearms, autobows, gauntlets, dual blades and greatswords, all of which have unique Nekaiyo-themed variants with skills and buffs suited to underwater play!