Fourth season of .

How can you fall in love when you can’t even hold hands? Due to a childhood curse, anything that the Duke touches will die—which makes his flirty maid’s behavior all the more shocking! Is there a way for the Duke and his companions to somehow break the curse, or is he doomed to a life where love is forever out of his reach?

Ayakashi are strange, supernatural creatures invisible to the majority of people. Though most are harmless, some ayakashi attack humans to devour their life force. Exorcist ninjas are tasked with protecting people from these spiteful spirits. Matsuri Kazamaki is a young exorcist ninja born to a prestigious clan. His childhood friend, Suzu Kanade, is an ayakashi medium—an individual with immense vitality that attracts ayakashi. Matsuri deems all ayakashi threatening and wishes to keep Suzu as far from them as possible, but this clashes with her desire to remain close to them. One day, the pair encounters Shirogane, the "King of Ayakashi," who is hellbent on consuming Suzu. As she is about to be eaten, Matsuri comes to the rescue and manages to seal the ayakashi's powers—but not before Shirogane takes revenge by turning him into a girl! Until he finds a way to transform back, Matsuri must adjust to his new, peculiar lifestyle while fighting against hostile ayakashi. Moreover, Suzu is now conflicted about her feelings toward Matsuri—further plunging their relationship into a state of ambiguity.

In 19th-century France, the wife of vampire noble Jean Duchet Godard is murdered in her own home. With the local human authorities unwilling to properly investigate the case, Godard hires a pair of private detectives known to specialize in the supernatural: Tsugaru Shinuchi, a man with a mysterious birdcage; and his partner, Aya Rindou. This enigmatic duo has come from faraway Japan for one purpose—to track down the man who stole both Aya's body and Tsugaru's humanity.