Both songs were used as opening themes for the
Mobile Suit Gundam: The Origin - Advent of the Red Comet anime; "Sora no Uta ~Higher and Higher~" was used from episode one until episode four, and "Hisōbi" was used from episode five until episode eight. A fan of the
Gundam franchise since childhood, lead guitarist
Sugizo was in charge of all of the anime's theme songs.
Ryuichi also grew up watching the franchise and said he wanted the songs' lyrics to fit the story. After discussions with the staff and Sugizo, he borrowed scripts from the show, watched videos over and over, and wrote down words that caught his attention. The vocalist recorded his parts for "Sora no Uta ~Higher and Higher~" before having surgery in January 2019 to remove
adenocarcinoma of the lung, while "Hisōbi" was recorded after. The music video for "Sora no Uta ~Higher and Higher~" utilizes footage from the anime as its lyrics feature connections to the fictional world of
Gundam. A different music video for the song using footage of the band performing it live at the
Nippon Budokan was also released. The music video for "Hisōbi" features the band performing the
ballad in
sand dunes with footage shot via a
drone by a Japanese
drone racing champion. ==Release==