

Even Abberline supports Administrator x Swan
Abberline and Swan did have feelings for each other.
However, Abberline accepted his fate. And while he wished that he could have been Swan's lover, he also accepts that even if it's not gonna be him, someone in that distant future (obviously, he's foreshadowing the Administrator because DUH!) will love Swan the same way or more than he did.
Hence, Swan Claire's current stance of being the Administrator's self-proclaimed biggest fan. But the Administrator is a Gacha MC - so even though Swan definitely has feelings for the Administrator (after you use Lifetime Contract on her, she has completely moved on from Abberline and is now officially part of the Adminitrator's harem, ESPECIALLY in her WEDDING Skin), we all know it's not gonna lead anywhere just like with other women in his harem of ladies.
But it also makes sense now why a lot of Koreans prefer Swan to be with the Administrator more than his other ladies.