Dayu Usukawa (薄皮 太夫 Usukawa Dayū?,) is Doukoku's right hand and the only one he is kind to, provided she knows her place as his obedient, unquestioning servant. Doukoku takes her in after her rebirth as a Gedoushu , giving her the name she now goes by and telling her that she has nowhere else to go but to him. But her unique origins set her apart from normal Gedoshu as she can move freely in the mortal realm. In life, she was Usuyuki (薄雪?) a shamisen player who obsessed over a man named Shinza. Scorned that he loved another woman instead of her, Usuyuki set fire to the building holding his wedding ceremony, killing him, his bride, and the entirety of their wedding party, in a suicidal crime of passion. Seeing that her love would remain unrequited to the bitter end, Usuyuki's emotions corrupt her soul and caused her rebirth into Dayu. The transformation also forcefully bonded Shinza's soul into the shamisen that Dayu carries with her, creating the eerie and unsettling songs that serve to soothe Doukoku's rage. The shamisen's headstock also doubles as the hilt of a shortsword Dayu uses in battle.
Of all the Gedoushu, Dayu has the most trouble getting along with the Ayakashi because of her previous life as a human, which she makes attempts to reclaim. One failed attempt results with her being saved by Juzo, developing feelings for the Gedounin as she begins to defy Doukoku's orders with her shamisen damaged as a result. Though her feelings for Shinza had long died, Dayu refuses to give him up as it would end her existence and desires to know the purpose behind it. Leaving Doukoku, Dayu wanders aimlessly until she is found by Akumaro who recruits her to his group in return for her instrument's restoration. Until it is repaired, she has to rely on the Sange Hankontō (散華斑痕刀?, Glorious Death Spotted-Scars Sword) dagger in her fights. Upon learning that Akamaro never intended to repair her instrument, she attempts to reclaim her shamisen until Dokouku comes to her aid, using a piece of his body to restore the shamisen and reminding her of her place by his side. Soon after Akumaro's demise, Dayu returns to the Rokumon Junk to assist in Doukoku's reawakening. To that end, after finally having the answers to her questions, Dayu deliberately has Shinken Pink destroy her shamisen to not only discard her past life, but to also use Shinza's anguished soul to revive Doukoku. She later uses the last of her powers to restore Doukoku's body, giving him immunity to the Sealing Character and independence from the Sanzu River. With only her kimono remaining, Doukoku later throws it into the Sanzu River as a final respect to her. Dayu is modeled after Benzaiten (弁財天?), a sea slug, and various molluscs and has elements of the futakuchi-onna (二口女?).
In the December 2009 issue of Hyper Hobby magazine, her name is mistakenly written in English as "Tayu".