The absorption ending is NTR and a BAD ending so it will never get more anything
Belle can come with you on any good ending
Belle's story is done and she is not in the next game being made, so her story is done.
PEACE
I know who the absorption spell is a bad ending but Belle missing from it it's kind weird
And i know who it can come with the MC in any good ending as well as not, but why Belle always have happy endings? the others have a lot of bad posibilities and endings, without even being a bad ending.
Besides the second thing who i asked
Belle was more a cosmetic end rather than an expansion, to avoid repetition and to fully exploit the only character who seems inmune to interaction, despite being talking all the time