Setsuna, also known as "Setsuna of the Moment of Dreams," is the Absolute Angel Claíomh Solais. She fights alongside Kyoshiro as his partner. Setsuna treasures a ribbon bow with bells, which is given to her by Kyoshiro and tied to the right side of her headdress. Rarely expressing any emotion, she is physically beautiful and can carry out every household chore flawlessly, leading Kū to call her a "princess". Setsuna acts solely based on Kyoshiro's orders and wishes, not her own will, and has a habit of saying, "Would you prefer that, Kyoshiro?" She begins to grow jealous of Kyoshiro and Kū's closeness, but she holds back her feelings so as to not trouble Kyoshiro. When Kyoshiro confesses his love for Kū, however, Setsuna fails to restrain her emotions for the first time, bursting into tears and expressing how she felt. Shortly after this, the trio was interrupted by Kazuya, who attacked Kyoshiro, leading Setsuna to put her woes aside in favor of attacking Kazuya. She was overwhelmed by his power and low on mana, knocked unconscious and kidnapped alongside a now amnesiac Kū. Shortly after, when Kazuya attempted to merge all of the angels together, she expresses her feelings that she must have done something wrong and been a failure somewhere along the line for Kyoshiro to treat her the way he did, expressing that she loved him with her whole heart... But did not wish for the destruction of the world, knowing he would not want it.
Soon after being freed, she appears to have come to terms with Kyoshiro loving Kū as opposed to her, stating she would leave him alone for the rest of his life as she was aware that was what he must have wished. However, she states she will first help him find Kū before departing.
In the end, she is shown witnessing the reunion of Kū and Kyoshiro, before presumably taking her leave and taking to wandering, alone.