I have already mentioned RuneQuest 6. It is the latest incarnation of the original RuneQuest rules, which gave birth to the Basic Role-Playing (BRP) system back in the 80s. And of course you know that The Celestial Empire uses BRP as its 'engine'.
Now the earlier version of RQ6 was called Mongoose RuneQuest II, which was re-released as Legend after Mongoose lost the licence to using the 'RuneQuest' name. There are many non-Gloranthan settings available for the Legend game, and one of these settings is called Samurai of Legend and lets you play in Heian Japan.
Mongoose has just made available on DriveThruRPG a free scenario for Samurai of Legend, which is really good. From the blurb:
Beneath and Opal Moon is an introductory scenario for Samurai of Legend characters. It takes place in an isolated village in a southern Honshu province and is designed for between three and five characters, which can be samurai, sōhei, a mixture of the two and include a priest.
The scenario should provide a couple of strong sessions of play and produce ideas for future adventures.
You can download the scenario and play it as is (Legend and TCE are highly compatible, as are all D100-based role-playing games), or you can adapt it to your Imperial Chinese campaign game with the following suggestions. Note: do not read the following if you are a player, as it contains spoilers.
- Set the adventure in Táng China— because of the nobility.
- Set the adventure in South China— because of the rice fields.
- Rename the families; Sakoda becomes Xīguō, Taira becomes Píng. Both are aristocratic families.
- sōhei (僧兵) are Japanese Buddhist warrior-monks with no Chinese equivalent; still, you can use the Buddhist Monk profession from p49 of TCE.
- kami (神) are Japanese nature spirits, again without any Chinese equivalent. For the scope of this adventure, however, the local kami can be replaced with the Village God (土地公 Tǔdì Gōng) and his wife, Earth Grandmother (土地婆 Tǔdì Pó). The Chinese Village God also has a shrine, like the Japanese kami, which is central to the religious life of the small community.
- rokuro-kubi (轆轤首) are human-looking yāomó that feed on live human flesh during the night. The GM can stat the rokuro-kubi using the stats of the èmó (p116 of TCE) with the following modification: INT 3D6, and with the following demonic features: Extensible neck (the neck can extend and the head can attack up to several metres around the creature, delivering a bite attack), and Regeneration at level 3 efficiency (p159 of BRP), or he can simply use the stats provided with the adventure. A description of the standard rokuro-kubi (without the detachable head and guts form) can be found here.
- A mujina (貉) is a sort of huòmó (p118 of TCE), except that her victim loses INT instead of CON characteristic points. The mujina in the adventure is quite intelligent (INT 14), much more so than the average huòmó.
- The fact that placing blood in a kami shrine would pollute it is a typical Japanese belief; however similar beliefs did exist in ancient China. The GM may either keep the same incident, or devise another one (the statue of the Village God has been broken, or refuse has placed on his altar, or a piece of his golden ingot has been chipped away...).
- Wandering Shinto Priest — to be replaced with a travelling Daoist monk. He's on a pilgrimage to Mount Qíyūn, one of the Four Sacred Mountains of Daoism.
- gaki (餓鬼) is the Japanese form of the Chinese word èguǐ (p125 of TCE).
- Replace the Lore (Shinto) skill tests with Knowledge (Religion [Daoism]) skill tests.
- Replace Purity with Daoist Allegiance.
- The Wild Man can be healed by the spirit of Tǔdì Pó or, as written in the adventure, by his wife's poetry or through a long period of spiritual healing in a Buddhist monastery.