inese ▁reg imes ▁accepted ▁Chinese ▁su zer ain ty ▁and ▁acknowled ged ▁the ▁Chinese ▁em peror ▁as ▁their ▁nom inal ▁over l ord . ▁Since ▁Chinese ▁em per ors ▁claimed ▁to ▁be ▁the ▁Son ▁of ▁Heaven ▁and ▁held ▁supre m acy ▁over ▁all ▁under ▁Heaven , ▁r ul ers ▁of ▁foreign ▁reg imes ▁were ▁to ▁use ▁titles ▁sub ordinate ▁to ▁em peror . ▁The ▁same ▁doctrine ▁also ▁maintained ▁that ▁there ▁could ▁only ▁be ▁one ▁em peror ▁at ▁any ▁given ▁time . ▁ ▁Japan ▁▁ ▁Chinese ▁em per ors ▁originally ▁referred ▁to ▁Japanese ▁r ul ers ▁as ▁the ▁King ▁of ▁Wa ▁( <0xE5> <0x80> <0xAD> 王 ). ▁ ▁During ▁the ▁S ui ▁dynast y , ▁the ▁Japanese ▁diplom at ▁O no ▁no ▁Im oko ▁delivered ▁a ▁letter ▁by ▁Prince ▁Sh ō to ku ▁to ▁the ▁Emperor ▁Yang ▁of ▁S ui ▁which ▁claimed ▁the ▁Em press ▁Su iko ▁as ▁" the ▁Son ▁of ▁Heaven ▁where ▁the ▁sun ▁r ises ", ▁imp lying ▁an ▁equal ▁status ▁between ▁the ▁Japanese ▁and ▁Chinese ▁monarch s . ▁The ▁Emperor ▁Yang ▁of ▁S ui ▁was ▁anger ed ▁by ▁such ▁a ▁claim . ▁ ▁During ▁the ▁Tang ▁dynast y , ▁Japanese ▁r ul ers ▁were ▁con ferred ▁the ▁title ▁King ▁of ▁Japan ▁( 日 本 國 王 ). ▁ ▁During ▁the ▁Y uan ▁dynast y , ▁the ▁Emperor ▁Sh iz u ▁of ▁Y uan ▁demanded ▁the ▁King ▁of ▁Japan ▁to ▁submit ▁to ▁him . ▁In ▁this ▁instance , ▁the ▁King ▁of ▁Japan ▁referred ▁to ▁the ▁Japanese ▁em peror . ▁ ▁During