Well, not yet, but in the earliest stages of doing so. I am in the process of re-developing my Kaidan setting of Japanese Horror for OSE (Old School Essentials). I am about to contract a designer/collaborator with extensive experience working with OSE. Aside from adventure material which will need created, as far as main books go, I see a
GM's Guide to Kaidan, as a pocket version of the existing GM's Guide to Kaidan (Pathfinder) focusing on the archipelago, important locations, history, etc. Then I think I need an
OSE Advanced Classes Guide for Kaidan, trying to shoehorn the various class types from Kaidan to best fit OSE rules, so somewhat simplified versions to capturing the range of classes that should be included (samurai, yakuza member, shinobi/ninja, yojimbo bodyguard ranger, onmyoji wizard, various clerics and monks, etc.) Something I never created for my PF version of Kaidan, but something still needed will be a
Kaidan Bestiary with 20 - 36 monsters and races.
Finally, closer to my main skillset, I plan to create one of more
Encounter/Map Books. A
Typical Kaidan Encounters book would include: a
roadside inn (ryokan), yakuza gambling den/brothel, formal bath house with inn, kabuki theater, teahouse restaurant, rural shrine, temple & garden, mikko shrine & cemetery, samurai walled manor, yakuza house, kimono/silk dyer house, sake brewery, typical rice farmer farm & home, Eta Physician Shop, typical mercantile shop, and a weapon smith. I could also see an
Exotic Encounters of Kaidan, with fewer, but larger area maps of specific unique sites in Kaidan, some of which were designed for the original Kaidan, but was never published, like: a
Lord's Castle and Palace (shiro),
Ryukyo the Seadragon city under the sea - home to samebito and merfolk, as well as the sea dragon,
Yomishima (Isle of the Dead) with a Kofun dungeon, abandoned shrines and many instances of undead, especially Japanese ghosts to contend with. A
Samurai Town, with full map and mapped locations within. A
forest village of henge, tengu and mountain folk.
I can use mapped locations created for the original Kaidan, but were never detailed enough with close-in maps of structures within such locations. Such as my
Nine Bridges of Akayama, tengu village map...