Bio: 14歳。琥珀こはくがお頭を務める妖怪退治屋に参加し、妖怪退治を生業にしている。実は4歳の頃、双子の姉のとわと別れ別れになったが、10年後、もろはと共に現代にタイムスリップ。とわと再会する。しかし、夢ゆめの胡蝶こちょうに眠りを奪われたため、幼い頃の記憶がない。とわが姉だと言っても信じない。せつなの眠りを取り戻そうとするとわともろはと共に、戦国時代に戻ることになるが……。冷静沈着で物事に動じない様は殺生丸譲りと思われる。

She's 14 years old. Trained as a Taijiya and led by Kohaku, who is also a Taijiya. When she was four, she lost her twin sister Towa, in a forest fire but 10 years later a time slip opened up and they were reunited. However, Setsuna had no recollection of her childhood because something stole her dreams. She didn't believe what her sister said about them being related. When she trys to get her dreams back, she winds up returning to the Sengoku Jidai, along with Towa ...Sesshoumaru is her father, and she's inhereted his calm, cool dispostion.