Sailor Moon: Moon Knight

Thousands of years ago on the moon, a civilization was destroyed and all of its subjects killed. In this civilization existed three special people: Princess Serenity, the future ruler of Silver Millennium, Monda, the royal seer and advisor, and Ayo, a white knight and bodyguard of Princess Serenity. Ayo and Serenity were especially close, as they were lovers when the kingdom was attacked. Ayo died protecting Serenity alongside close ally and friend Prince Endymion. Years later, the three were reencarnated as three teenagers on Earth: Serenity as Usagi Tsukino, Monda as Kenmeina "Ken" Tsukio, and Ayo as Shiroi Tsuki. After Usagi meets a cat named Luna, the three begin to remember bits and pieces of the past.