"One" is the thirteenth single by Japanese singer Aimer, released on October 11, 2017 under SME Records.

Written by Aimer (under her pen name "aimerrhythm") and Rui Momota, the single peaked at No.

She explained that "One" was a new chapter in her career after her compilation album Best Selection "noir" ended with the song "zero.

[5] The single includes "Hana no Uta" (the ending theme of Fate/stay night: Heaven's Feel I. presage flower), "Rokutosei no Yoru Magic Blue ver."

[8][2][9][5] The music video for "Hana no Uta" was directed by Takahiro Miki and features actress Minami Hamabe.