During the final battle in what was once the fair town of Sunnydale, California. Buffy Summers and Willow Rosenburg created a spell to make all the potential slayers of the world into full-fledged slayers. Satsu is among these young women who received the gifts of a slayer.
Little is known about Satsu only that she is among Buffy's three favorite slayers and may even be Buffy's favorite among all of them. Satsu's opinion of Buffy however may be even greater than Buffy's opinion of her. When Amy, a former friend now enemy of the Scoobie gang casts a spell on Buffy that entraps her in her sleeping state it is Satsu (though no one but her knows this) who breaks the spell by planting a true love's kiss on the sleeping Buffy. Though the kiss is not actually seen by any of the characters or the readers for that matter the kiss itself was subtly revealed by the issue's writers. Buffy awakens with the taste of cinnamon buns on her lips but quickly forgets about it at the sight of her best friend Willow in her room. When Buffy and Willow catch up on old times while on guard of an unconscious Amy, Buffy brings up the subject of who broke Amy's spell before anyone can answer Willow is pulled into a magical trap and the question "Who kissed Buffy?" is forgotten once more. When a mission is set to rescue Willow, Buffy chooses Satsu to accompany her. Before they begin the mission Buffy turns to Satsu to borrow her lip gloss. After applying the gloss Buffy takes a look at it and says, "Hnh. Cinnamon" not quite realizing that it was Satsu who had kissed her but revealing this fact to the comic's readers.
Later in the series Buffy confronts Satsu and tells her though she is flattered she cannot return Satsu's feelings. Buffy and Satsu experiment with Buffy's sexuality but in the end it is clear that Satsu cares more for Buffy than Buffy does for her. After another "experiment" Satsu stays in Japan to train the new slayers there while Buffy goes back to Scotland.
A few issues later (issue number 22) Kennedy is sent to do an evaluation on her. Satsu assumes Kennedy was picked for this job because they`re both gay but Kennedy confesses she asked for it. She seems determined to at least attempt the girly-bonding thing and genuinely wants to help Satsu both get over Buffy and become the best Slayer she can (as corny as that sounds).