▁ik iry ō ▁possessed ▁Gen ji ' s ▁wife , ▁ultimately ▁leading ▁to ▁her ▁dem ise . ▁Upon ▁real ising ▁that ▁her ▁je alous y ▁had ▁caused ▁this ▁mis fort une , ▁she ▁locked ▁herself ▁away ▁and ▁became ▁a ▁nun ▁until ▁her ▁death , ▁after ▁which ▁time ▁her ▁spirit ▁continued ▁to ▁ha unt ▁Gen ji ▁until ▁her ▁daughter ▁performed ▁the ▁correct ▁spiritual ▁r ites . ▁ ▁Ha unt ings ▁Y ū rei ▁often ▁fall ▁under ▁the ▁general ▁um bre lla ▁term ▁of ▁ob ake , ▁derived ▁from ▁the ▁verb ▁b aker u , ▁meaning ▁" to ▁change "; ▁thus ▁ob ake ▁are ▁pre tern atural ▁be ings ▁who ▁have ▁under g one ▁some ▁sort ▁of ▁change , ▁from ▁the ▁natural ▁real m ▁to ▁the ▁super natural . ▁ ▁However , ▁y ū rei ▁differ ▁from ▁traditional ▁b ak em ono ▁due ▁to ▁their ▁temporal ▁specific ity . ▁The ▁y ū rei ▁is ▁one ▁of ▁the ▁only ▁cre atures ▁in ▁Japanese ▁myth ology ▁to ▁have ▁a ▁preferred ▁ha un ting ▁time ▁( mid time ▁of ▁the ▁hours ▁of ▁the ▁Ox ; ▁around ▁ 2 : 0 0 am - 2 : 3 0 am , ▁when ▁the ▁ve ils ▁between ▁the ▁world ▁of ▁the ▁dead ▁and ▁the ▁world ▁of ▁the ▁living ▁are ▁at ▁their ▁th inn est ). ▁By ▁comparison , ▁normal ▁ob ake ▁could ▁strike ▁at ▁any ▁time , ▁often ▁dark ening ▁or ▁changing ▁their ▁surr ound ings ▁should ▁they ▁feel ▁the ▁need . ▁Similarly , ▁y ū rei ▁are ▁more ▁bound ▁to