Hourai is an island shrouded in mystery, emerging only once every half-century. Some say the isle holds the secret to everlasting youth, while others fear it brings ruin to their lands. When Inuyasha's crew rescues a young half-demon girl named Ai from a fearsome monster, she reveals that she fled Hourai. In a shocking twist, Ai turns out to be an old acquaintance of Inuyasha's and pleads with him to save her captive friends, held by the Four War Gods - an old enemy of Inuyasha’s. Upon arriving at Hourai, the team discovers that the only inhabitants left are a handful of orphans, destined to be used as sacrifices to boost the Four War Gods' power. Adding to their woes, the children bear enchanted markings that prevent them from escaping. With no other option, Inuyasha must defeat the four demons, but their incredible strength makes it a daunting task that can only be achieved through the group's combined efforts.