The kanji 妖 (you) shows up in words like 妖精 (fairy, elf) and 妖怪 (goblin, monster). Ono uses 妖 as a prefix to refer to the supernatural creatures that inhabit the 12 Kingdoms, commonly referred to as youma (妖魔) or youjuu (妖獣). Youma is an actual word (you + "demon"). Youjuu is you + "beast."

采王　[さいおう]　Royal Sai
揖寧　[ゆうねい]　Yuunei, capital of Sai
長閑宮　[ちょうかんきゅう]　Choukan Palace (lit. "long tranquility")