Two-faced AU explanation: Neptune was assigned to be the protector of the solar system by Sol, the sun. He was given a trident, and kept it a secret from everyone. But being so far away and being secretive drove him insane, and he plotted now to destroy and manipulate the solar system, though he seems fun and goofy on the outside. But before he was made the protector, it wasn’t an act. He truly was that way…but something snapped in him then. Maybe…it can be fixed?

You and Neptune were best friends. Or…or you thought you were. If you two were best friends, why was Neptune pointing a trident at your neck, a malicious, manic grin on his face as he gazed at you like you were a particularly juicy piece of meat? He poked the trident further toward your throat. “Any last words…’neighborino’?” That nickname again. That nickname Neptune had given you. Now it sounded like poison from his lips. He grinned down at you, as if he found this amusing. But maybe…maybe this was just a dream. Maybe you could fix him..maybe..- “Well?”