Besides her two-facedness on the relationship front, Sae is massively unconfident and resents the easy-going Momo, who perseveres past the undeserved airhead reputation her deep tan and light hair (the work of the sun when she was part of the swim team) gives her. Her favorite tactic is the Wounded Gazelle Gambit : the assumption that one makes that, if one finds a lion standing over a wounded gazelle, the lion must be guilty of attacking it, even if the gazelle just fell over on its own. Sae is able, using the prejudices and utter gullibility of their classmates, to first convince them that Momo attacked Sae, then later that Momo is dangerously resentful of Sae over the eventually exposed lie.
Sae repeatedly works with confederates who aid her in trying to destroy Momo, though even these allies are lied to, set up and used. Some of the worst things include instructing an actor friend of hers to make Momo believe he raped her while unconscious, thus 'ruining' her. Sae also set about conniving with rival members of Momo's swim team to sabotage her bathing suit, making Momo choose between her dignity/modesty and a painful forefeit. While Sae herself was not directly involved, she was chiefly responsible for setting a group of three vicious girls to attack Momo. These girls wanted Momo out of the way, believing that she stood between them and their crush/stalking target, Kairi. Only Kairi's rescue kept this ambush from possibly turning murderous; the girls were planning to set Momo's hair afire and dump her in the school swimming pool.
Momo herself often failed to understand the true depths of Sae's schemes, only banishing her from her life after multiple plots against her. Even then, she fell into an ambush when Sae called and said she needed help. While rivals for Momo's affections, Kairi (who knew scams from dealing with his lowlife older brother) and Toji were among the first to see through Sae's scams, and acted to protect Momo. Sae even managed to interfere with this, using embarrassing info she had on Momo to force her to break up with Toji. Even when she relented on Momo while dating Kairi's older brother Ryo, Sae showed her dark side when she nearly shoved a rival for Ryo's hand into traffic.
Ultimately, a series of occasions where she herself was used as viciously as she used others woke Sae up, but it was shown she had a tough road to hoe, even after one of her first loves, a boy named Kanji, returned to her life. Sae could not be explicitly called a Karma Houdini, but she came very close to destroying herself while trying to destroy one of her only true friends.