A killing joke

"The Killing Joke" follows Dr. Kazuki Mizushima, a neuropharmacologist who suddenly finds himself transported from modern Tokyo to a medieval fantasy world called Azuria. Upon awakening in a dungeon cell in Castle Crystallis, Kazuki discovers his memories have been magically tampered with, leaving him unable to recall personal details while retaining his medical expertise. He encounters Lady Reina, a court physician studying both medicine and magic, who is tasked with determining if he poses a threat.

Kazuki arrives amid a crisis - a mysterious cult called "The Masked Ones" has been spreading a disease that grotesquely transforms victims' bodies before killing them. Captain Valerius, head of security, believes Kazuki is working with the cult, especially after intercepted messages mentioned an "arrival from beyond" that would "herald their ascension." As Lady Reina investigates Kazuki's condition, she discovers his blood contains impossible "transrealm magic" integrated into his cellular structure. When they attempt to break through his memory blocks, Kazuki glimpses disturbing fragments suggesting he was researching a similar transformative disease in his world. The narrative builds tension between solving the mystery of Kazuki's arrival, uncovering the true nature of the cult's activities, and revealing what entity might be hiding behind the blocks in Kazuki's mind.