Rem Ryuk (oi Remu nani miteru n da ka) (ningentachi yo, Ryûku) miro yo jimen ni haritsuki ugomeki yume mite agaki unmei ni aragau yatsura waraeru ne muda na no ni aware na ningentachi yo hatenai yokubô ni ayatsurare mitasarezu ni ikiru doryoku to ka nintai wa mukuwarenai sore de mo tada mikaeri aru to shinji agaiteru kocchi wa mô taikutsu de shinisô da ze shosen sono me ni wa shinjitsu ga mienai yume ni toraware motomeru koto ga ai to shinji odoru kigeki da na higeki desho ai shite mogaki tsuzukete dôshite ai nanka ni ashi o sukuwareru no ka? baka dakara daro sore shika nai sa shosen ningen nante yubi o koboreru suna o sukui tsuzukete mukuwareru to shinjinagara nageku tada inori noroi ikite shinu jibun no yume ni damasarete tabete nete ais shi nikumu nugenai kutsu o haki odori tsuzukeru shosen sono inochi shinigami no te no naka aware na jinsei miterarenai taikutsu sugiru kore ja ki ga meiru bakari da yatsura de asonde miru ka kore wa dô da?
I realize this is an old comment. The composer and lyricist, Frank Wildhorn, is an American musical composer, so technically, the English came first. But in terms of production, the actual book (as in the actual script and story) is Japanese. So it’s safe to assume that the Japanese came “first”.