SAKURA WARS: ~SU~MI~RE~

Set after the time of Sakura Taisen 4 (game), Kanzaki Sumire, during a training session was noticed that her spirit power (rei-ryoku) has dropped tremendously, below levels required to pilot the Koubu-nishiki. She decides to retire from the Kageki-dan while she still holds the position of "top star" in the dai-teikoku gekijyou. (Source: Anime News Network) — Description from AniList community (anilist.co).