Sayoko
Sayoko Mishima, previously the most beautiful, popular girl on the Nekomi Institute of Technology's campus, has a few bones to pick with Belldandy. She was the most beautiful, popular girl of her own little college kingdom - before Belldandy showed up. She also previously wore the crown of the Nekomi Tech Campus Queen - again, before Belldandy showed up, and in her good-natured, slightly bumbling way, stole the crown the year that the Nekomi Tech Motor Club ran the contest. Previously the Queen of the campus in every meaningful sense of the word, Sayoko suddenly found herself dethroned, and angry. Since the earliest chapters of the manga, Sayoko has been hell-bent on beating Belldandy (in any way possible) and regaining her place as the alpha female on campus. But no matter how much Sayoko wiles, she never does truly succeed in humiliating or defeating Belldandy... Which only makes her desire to do so grow stronger every day.
It seems inevitable, then, that the demon Mara would be drawn to the side of a human who so venomously wished Belldandy ill.
Sayoko wakes up one morning to find a strange woman sleeping in her bedroom, and realizes with panic that she has no memory of where she was, or what she was doing, the previous night. The woman turns out to be Mara, and she introduces herself to Sayoko as a Demon, First Class. "Your psychic emanations called me to you," Mara tells Sayoko. "Let's make a deal. You want to get rid of Belldandy, don't you?"
As soon as Mara mentions Belldandy's name, Sayoko's face twists into a mask of rage that causes even Mara to become momentarily frightened.
Mara first enlists Sayoko's aid in fetching the Demons CD from Belldandy, and then engages in a series of small plots designed to help Sayoko seduce Keiichi away from Belldandy. Mara crashes at Sayoko's place during her first introductory chapters of the manga. Later, however, after Mara's first few plots prove unsuccessful and Urd defeats her by forcing her to listen to disco music and dance until she is exhausted, Mara apparently takes her leave of Sayoko. Chapter 29 opens as Mara emerges from a long, restful sleep in an anonymous coffin, obviously no longer in Sayoko's home; she is not seen together with Sayoko again until much, much later in the manga.
Surprisingly enough, during Mara's long absence in the chapters following the Lord of Terror arc, Sayoko grows and matures somewhat as a character. But first she self-destructs and crashes completely, suffering a personal crisis that culminates in her showing up at Keiichi's house in the wee hours of the morning, smashingly drunk, ringing the bell of the shrine and screaming nonsense at the top of her lungs, clutching a bag full of take-out food that she offers to Keiichi the moment he shows up at the bell. Then Sayoko proceeds to collapse into Keiichi's arms and sob.
Thankfully, the Queen soon recovers her sobriety, and her dignity. And as she ends up spending a little bit of time in Keiichi's company, she begins to notice something that she didn't see before - Keiichi really is a special guy.
From the beginning, it seemed as though Sayoko was only interested in Keiichi because she wanted to steal Belldandy's boyfriend, and humiliate her. Sayoko was never actually attracted to Keiichi, at first. "I can make a fawning slave of a wimp like that in three days flat," Sayoko brags to a friend in chapter 5. Later, she tells Mara, "My goal is to get rid of Belldandy, that's all. Keiichi's just a means to that end." But even as Sayoko's continued efforts to steal Keiichi fail, she only ends up getting to know him better, which causes an unexpected change in her heart. "Me? Falling in love with that little dweeb?" Sayoko asks herself almost rhetorically in chapter 44.
Sayoko's attitude toward Keiichi may be changing, but unfortunately, her desire to best Belldandy only grows stronger with time. Mara is once again drawn to Sayoko's side in chapter 81, when she hears Sayoko wish to be crowned Campus Queen in the upcoming annual competition, winning her previous crown back from Belldandy. "How can she be praying for something so pointless and stupid," Mara wonders to herself, "with that much sincerity and mind-force?" But nevertheless, Mara senses the powerful force of will behind Sayoko's wish, and offers Sayoko the opportunity to sign a contract with her. Sayoko, ever the shrewd negotiator, does refuse to sell her soul to Mara. But she agrees to pay an unspecified price, sometime in the future, in exchange for Mara's help.
Although the results of Sayoko's wish naturally turn out to be disastrous, the Queen Sayoko story arc gives Sayoko the chance to articulate her complex toward Belldandy in a way that she never has before. At the end of chapter 85, Mara finds that her desire to defeat Belldandy by sending her back to Heaven differs significantly from what Sayoko wants for Belldandy. "What I want," Sayoko tells Mara, "is to defeat Belldandy. I want to see her crushed, spirit broken, weeping at her failure. I don't want her to go away-- I want her around so that I can gloat!" A few panels later, Sayoko looks at Belldandy and thinks, "If you're not here... I'll have no competition! I'll die of boredom!" Believe it or not, Sayoko's statement may not be all that different from the way that Mara feels either. As nasty as Mara really is, and despite all the awful things that she does to Belldandy and Keiichi, one does get the impression that Mara, too, would be pretty bored without Belldandy around to focus her efforts on. Second, Mara seems ultimately unable to forget her childhood friendship with Belldandy... And Sayoko, similarly, is unable to bring herself to completely dislike Belldandy. She genuinely admires certain aspects of Belldandy's character, a fact which becomes more and more evident as the manga progresses.
So why do both Sayoko and Mara do such awful things to people that they both, in their own twisted ways, actually care about? Ultimately, both are using Keiichi and Belldandy as means to their own ends. Sayoko wants Belldandy defeated but still sticking around, just so that she has competition and somebody to gloat around; Mara wants Belldandy defeated and gone away for good, so that she can improve her ranking in Hell. So despite the differences, both are united by the common goal of besting Belldandy. And both of them use poor Keiichi as means toward that end, although Sayoko seems to be more concerned with seducing him, whereas Mara would be happy just to see him turned into a lizard or suffering some similar horrible fate. Together, both Sayoko and Mara make a formidable pair. Sayoko is just about as close to a demon as a human woman can be.
In chapter 75, while Sayoko is walking around campus one day during summer break, she finds her thoughts turning toward Belldandy yet again. "I know it's summer break, but still, she hasn't been around at all. I miss the tension! Let's see some sparks fly! C'mon, Belldandy! Come out and fight!" Personally, I think that Sayoko's words here are probably not all that different from the way that Mara normally feels about Belldandy, either. It's Mara who always seems to be going out of her way to seek out and bully Belldandy, especially in the earlier chapters of the manga.
Sayoko and Mara are like two sides of the same coin. Both of them focus on beating Belldandy; neither of them hesitates to manipulate Keiichi as a means toward that end. But despite all of that, both Sayoko and Mara share the fact that they harbor complex feelings toward Belldandy (and in Sayoko's case, Keiichi too) that conflict with their often villainous plots against her. I wouldn't hesitate to label these two women, together, as the most complicated antagonists in the series; and that just makes these characters all the more interesting and likeable, doesn't it?