On September 25, 2021, LiSA's official website announced that she would be performing the opening and ending themes for the anime Demon Slayer: Kimetsu no Yaiba – Mugen Train Arc premiering on October 10, 2021, with "Akeboshi" as the opening theme and "Shirogane" as the ending theme. Both songs were released as a double A-side single on November 17, 2021. Prior to the single's release, "Akeboshi" is available for download from October 18, 2021.[3][4]
"Akeboshi" is composed in the key of C-sharp major and is set in time signature of common time with a tempo of 95 BPM, runs for four minutes and 29 seconds.[5] Written and composed by Yuki Kajiura,[6][7] the song starts with strings in the intro, giving off an atmosphere of fantasy, melancholy, and mystery; then a guitar riffs reverberates through the middle of the song. The melody is reminiscent of Aimer's song "I Beg You" which also composed by Kajiura.[8] LiSA describes "Akeboshi" as a song of entrusted thoughts, hopes and curses.[9]
The music video for "Akeboshi" was released on November 7, 2021, and directed by Masakazu Fukatsu. Based on the world view of the song, it expresses "a hope in the midst of chaos". It shows LiSA performing the song in a railroad tunnel illuminated by lanterns and on a lawn surrounded by flames at night, mixing with images of liquids called "Alive Painting" created by painter Akiko Nakayama.[9][10] As of May 2022, "Akeboshi" has over 20 million views on YouTube.[11]
^"10/10(日)23:15~放送開始のテレビアニメ「鬼滅の刃」無限列車編オープニングテーマとエンディングテーマを担当決定。 11/17(水)に両A面シングル「明け星 / 白銀」のリリースが決定。" [The opening theme and ending theme of the TV anime 'Demon Slayer: Mugen Train Arc', which will start broadcasting from 23:15 on October 10 (Sun), will be decided. Both A-side singles "Akeboshi / Shirogane" will be released on 11/17 (Wed)] (in Japanese). LiSA Official Website. September 25, 2021. Retrieved October 23, 2021.
^"「鬼滅の刃」無限列車編が新作エピソード加えTVアニメに!" ['Demon Slayer: Mugen Train Arc' is now a TV anime with new episodes!]. Natalie (in Japanese). September 25, 2021. Retrieved October 19, 2021.