"Eien" (永遠, Eternity) is Zard's[1] 22nd single released on August 20, 1997 under B-Gram Records label.
Junichi Watanabe, the writer of the novel, wrote the title word "Eien" of the CD cover. The single reached rank number 1 first week. It charted for 13 weeks and sold 628,000 copies.[2] When Izumi Sakai died in 2007, it was selected as her fifth best song on the Oricon polls.[3]