Dakuen echoes the monk Ryoan from Takeshi Narumi and Sho Aikawa's 1987 OVA series Sengoku Kitan Yōtōden. Their introduction scenes are both in order to save the main lead from a supernatural ninja, both appear and disappear at chance, and both are related to devils either symbolically or literally. Dakuan's hat and kimono are directly based on those worn by Ryoan.
Kagero is an Expy of Ayame from Sengoku Kitan Yōtōden, another kunoichi who fights with a kodachi, seeks revenge for the death of all of her team, and is forced to team up with a washed up ninja swordsman and a diminutive monk.
The Devils of Kimon are taken from the seven Oboroshi ninja from Sengoku Kitan Yōtōden, being a number of rogue ninja with supernatural powers who seek to cause political changes in Japan.
Dakuan also resembles Giuseppe Mayart from Kawajiri's previous work Wicked City, being a creepy little old man with an unpleasant personality who manipulates the male and female heroes to have intimate contact with each other. Fittingly, the two characters were voiced by the same actor in the Spanish dubs.
Film
Mujuru is an Expy of Ichi from Zatoichi, the most famous blind samurai in popular culture.
Literature
While Jubei was a real samurai, his portrayal here owes a lot to Futaro Yamada's works Yagyū Ninpōchō and Makai Tenshō.
Dakuan resembles the historical monk Takuan Soho, though very much like Jubei, specifically Takuan's portrayal in Futaro Yamada's Yagyū Ninpōchō. His malicious personality and ambiguous relationship with Jubei are taken from this one.
Kagero's name and poison affinity (yet only those, as she is quite different otherwise) are taken from a character from Futaro Yamada's Kōga Ninpōchō.
Genma echoes Yakushiji Tenzen, the ruthless, power hungry Big Bad with immortality powers of Kōga Ninpōchō, though only in general lines.
Tessai is an Expy of Gyobu Kasumi from Kōga Ninpōchō. Like Tessai, Gyobu is a bald giant whose powers allow him to turn his body into inanimate materials yet is oddly specialized in stealth as well.
Benisato is reminiscent of Hotarubi from Kōga Ninpōchō, another kunoichi associated with both snakes and illusion spells.
Mujuru is Shuranosuke Sakaki from Takeshi Narumi's novel series Shuranosuke Zanmaken, only blind. Mujuro's robe design and style evokes Shuranosuke's from the 1990 OVA adaptation, where the latter even keeps his eyes closed very often.
