500 years ago in the Tensho Era of Japan, a man was born who defied the will of a demon; a man who had gods of good on his side; a man destined to battle evil....his name was Kabuto. Somehow, Kuroyasya Douki, the vile Black Night Demon, escaped his prison in hell and returned to the earthly plane to wreak vengeance on the family-line of Kabuto. None can escape his deadly magic and masterful skills with the blade; however, the gods of the North, West, East, and South band together to help Kabuto stand for Justice. With the questionable help of a diabolical talking sword that his own father forged, Kabuto may live another day to see his own sons born....

Kabuto is a tengu who has to save a princess from fortress which is full of monster-mecha hybrids in an alternate reality of feudal Japan.

The episode bundled with the 13th volume is about the Sumo competition that held at Tempest for the first time, suggested by Rimuru. The three-part OVA bundled with the 14th, 15th, and 16th manga volumes is an original trilogy written by Fuse. Rimuru has been teaching Shizue's students at Ingracia Kingdom's Freedom Academy. The time has come for the school's annual outdoor training event, where the students will test their combat skills in the field. Rimuru is determined to win the competition and take home the prize money, but he is challenged by Jeff, an honorary teacher who sees Rimuru as a rival. The competition is underway when suddenly an unexpected enemy appears!

Jubei Kibagami wanders feudal Japan as an itinerant swordsman-for-hire. After a past betrayal left him masterless, he has no more patience for warring political factions and their schemes. Unfortunately, both past and political intrigue collide when he meets and saves a female ninja named Kagero from a man with the ability to make his body as hard as stone. The sole survivor of a ninja clan, Kagero continues her team's last mission: investigate a mysterious plague that wiped out an entire village. Jubei wants nothing to do with this, but the stone-like man's allies, a group of ninja with supernatural powers known as the Devils of Kimon, make that option difficult. To make matters worse, a government spy poisons Jubei, promising him an antidote if he can unravel the true intentions of the Devils of Kimon and their connection to the plague. The trail leads to shadow leaders, a plot to overthrow the government, and a man that Jubei thought he would never see again.