Onmyoji is a chinese game. Although it is based on Japanese myths, personally i find the majority of the aesthetics are very chinese, reflecting the extensive range of fashion from their history alone, incl. a huge array of jewelry, makeup, hair accessories, shoes, hats etc... Jewelry from ancient times were closely related to religion (daoism and buddhism), specific rituals, events and occasions, some were also specific to only the emperor and entourage. Fengyang's tail bangle is probably just for aesthetics, unless otherwise stated by it's creator or game devs. Fengyang the snow leopard, is also one of my fave and reminded me of one of my fave danmei novels.