I think I can understand that! While Aoi does get karma in the true end, and Kyouko/Mimiko do get a happy outcome as well, it isn't outright shown, so it may not be as impactful there...
Unhappy End is honestly one of my favorite endings from a literary standpoint, even if there is still that element of unknown tragedy surrounding Kin/Kira's outcome.
Getting to write all the characters interacting in such a tense situation was a treat. I'm glad to hear you enjoyed reading it :D