Theory[spoiler discussion]

There are strong indications that connect both characters. Origin: It is known that Flugel came from another world (Earth), just like Subaru. The Pleiades Tower: Flugel named the Pleiades Watchtower in honor of the star cluster that in Japanese is called Subaru. Furthermore, the trials within the tower require modern (Earthly) knowledge, which Subaru manages to solve. Shaula, the tower's guardian, immediately recognizes Subaru as her master, Flugel, due to his scent. A widespread theory is that Subaru is Flugel's reincarnation or amnesiac past self, though some theorize that they could even be the same person traveling through time to save Satella. Does Subaru want Emilia's body for the Witch of Envy? This idea arises from the moments when the Witch of Envy takes control of or possesses Emilia, but it is not a conscious action on Subaru's part. Satella's (the Witch of Envy's) obsession with Subaru and her Return by Death ability stems from a vow and a promise he made to her in the past to save her. The Witch's intentions toward Subaru are those of a possessive and twisted love. Many of the tragedies and possessions occur as "punishment" or a warning from the witch when Subaru attempts to reveal the secret of her ability, not because Subaru is actively seeking to resurrect her.