To kick off the season, a special episode titled "Digression: Diablo's Journal" will release on March 30, recapping the events of Season 2 from Diablo's perspective.

Girls study at schools for modern shinobi. They dedicate their entire young lives to learning to become true shinobi, battling each other to polish their skills. And then one day, Asuka, whose grandfather is a legendary shinobi, encounters an ancient evil being named a "Youma" in the back alleys of Tokyo at Christmastime. Where there is light, there is shadow. Over 28 of the strongest and most well-endowed ninjas in history, both good and evil, will collide in a battle to determine true justice. And this deadly battle begins... right now. (Source: Crunchyroll)

With Tenseiga having been broken by a spiteful Zero, Towa begins to infuse the heavenly healing sword with her limited amounts of demonic energy in order to revive Setsuna. Totosai and Jaken arrive at the scene, and Totosai states that he needs three whole days to mend Tenseiga. Unfortunately, by that time, Setsuna's vital essence will have been already sent to the Underworld, thus rendering the repaired Tenseiga powerless and that they have no other option but to rely on Towa's own demonic strength and will. While Towa struggles to utilize Tenseiga's heavenly abilities to try and save her twin's spiritual essence, Totosai retrieves the hilt of Setsuna's broken naginata and begins to restore it to create the blood bade she inherited from being one of Sesshomaru's half-demon daughters, the Yukari no Takichri. This greater infusion of a blend of pure demonic and mystical energy attracts a mass of demons both living and deceased. Moroha utilizes her somewhat stronger and more effective spiritual powers to purify a few dozen demons all at once with one single arrow alone, with backup from Kiara, but the two are largely outnumbered by their fellows. As the horde of demons' turn their attention to a concerned Sesshomaru and his unconscious twin daughters, the recently resurrected Setsuna awakes upon her name being said by her father, who fiercely holds her greatly advanced and upgraded naginata aloft, the Yukari no Tachikiri, and easily slays the demons, which Moroha and Kiara had not been able to do away with, in one single stroke. Sesshomaru then hands the broken Tenseiga to Totosai for its three day mending, and leaves with Jaken. Before leaving himself, Totosai warns Setsuna to never let herself be murdered again as the Tenseiga can only return sentient beings, human or demon, to life only once. While Towa remains unconscious from having drained herself of all her demonic energy to resurrect her twin sister, Totosai instructs Setsuna on how look for a mystical Kyuyokon root from the 214 year old Magnolia demon tree Bokusenoh to receive a proper demonic weapon for Towa, in place of the Kikujomonchi that she has been foolishly wielding since her return to the timeline of her birth.

Two planets, one to the East and another to the West, were once bound together by a chain called the Dragon Stream. But now, that chain is broken and the two halves are only joined in war. Nobunaga the Fool is heir to the Eastern Country of Owari. Regarded as too foolish and carefree by many, including his friends, Nobunaga is thought to be a nuisance even by his father. A girl from the West named Jeanne Kaguya d'Arc has visions of a "Savior-King." She is accompanied by Leonardo da Vinci as she journeys to the Eastern Planet in search of the person in her visions. Leonardo and Jeanne quickly fall victim to a military confrontation between powerful mecha, only to be saved by Nobunaga. Nobunaga takes control of Leonardo's mecha, intending to warn his family of the siege he suspects. Jeanne suspects that the lackadaisical Nobunaga might be the Savior-King she's envisioned.