Plutia is the predecessor of Neptune.
Plutia's appearance looks similar to Neptune in certain areas, but for the most part it looks as if she is dressed in pajamas more so than regular clothes. She has long, light purple hair in a braid to the back and light pink frill ribbon tied to it. Her eyes are magenta in color and she wears a white choker like Neptune's around her neck. Her dress is teal with a mix of pink, white, and light orange with thigh high socks and bear slippers to match.
Plutia is very calm, almost to the point of always seeming tired. This is most noticeable by the fact that she speaks rather slowly. She is kind and somewhat of a ditz but with minor sadistic tendencies. Much like Neptune, she tends to leave her duties as goddess ignored and spends most of her time either sleeping, making dolls, or playing around with Neptune. Plutia, also like Neptune, makes friends very easily due to her relaxed and caring nature.
Iris Heart's appearance in this form is akin to a dominatrix. Her hair becomes iris blue while her eyes turn into a slightly darker shade of magenta. She wears a black, one piece bodysuit with high heels and traces of magenta on the legs, torso, and arms which is also accompanied by a set of matching earrings and a choker.
Iris Heart is the goddess form of Plutia. Not only does her voice change (in tone and tempo), but her personality does too. Iris Heart, simply put, is a sadistic dominatrix which earned her the name “Sadie” from Neptune. Everyone tries their best to keep her out of this form due to her actions always proving to be bone-chilling and frightening to enemies and allies alike. While she is sadistic in this form, she still retains Plutia’s caring aspect as well, but just shows it in a different way.
Superdimension Neptune VS Sega Hard Girls