well if 당신 watch advent children complete the white light is there and zack is standing behind him and 구름, 클라우드 says "i am your living legacy" then he defeats sephiroth
당신 need to play Crisis Core to understand that...after 구름, 클라우드 defeated Sephiroth..he and zack woke up in a laboratory where dr.Mojo planted Sephirots sells to zack and 구름, 클라우드 and made a new Project...it's kinda weird but u need to play crisis core to understand...anyway excelent game...the whole FINAL 판타지 7 :D