Neptune Vasilias is a minor character in Project Yellow and a member of Team SSSN. His weapon of choice is a gun that can transform into a guandao or a trident.

Neptune is shown to be a calm, collected, and respectful individual with a carefree personality. He maintains a positive impression with people he meets and often hangs out with his friend Sun Wukong, who describes him as being cool.Neptune is prone to flirting with girls. He's shown to be fashion-conscious, aside from fitting the stereotypical popular guy image, he may have an intellectual side as well. Despite his cool demeanor, Neptune is very self-conscious of his image and can be easily embarrassed over his minor inadequacies, like his inability to dance, and refused to admit his fear of water. His tendency to protect his reputation can sometimes make him inconsiderate to the feelings of others. Despite his cool demeanor, Neptune is very self-conscious of his image and can be easily embarrassed over his minor inadequacies, like his inability to dance, and refused to admit his fear of water. His tendency to protect his reputation can sometimes make him inconsiderate to the feelings of others.