Bishoujo Senshi Sailor Moon Cosmos

Usagi Tsukino and her friends are living peaceful lives as ordinary high school students. Mamoru Chiba, Usagi's boyfriend, is headed to America to study abroad. At the airport, after Mamoru proposes to Usagi, he is then mysteriously extinguished by someone's hand. Unable to accept Mamoru's disppearance, Usagi hides her memory of that event. Meanwhile, Shadow Galactica, led by Sailor Galaxia, as well as Sailor Starlights appear in front of Usagi. Without knowing whether Sailor Starlights are allies or enemies, the Sailor Guardians are robbed of their Sailor Crystals, the source of their power, by almighty Sailor Galaxia, and are killed by one after another. In a hopeless situation, Usagi, as Eternal Sailor Moon, challenges Sailor Galaxia for the final battle.

(Source: AniList.co)