From everything I have seen (on Steam and the Discord), all the endings are sad. Someone said that they aren't bittersweet, they are just bitter and I kind of need to agree. I haven't had any ending so far that has been satisfying.
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Ya I'm guessing most of the endings will be more tragic. We'll have to wait and see till all routes have been attained. I feel personally my ending with Randal was more bitter sweet, but it does depend on how one portrays such feelings. However, a general happy ending would be nice, if we're gonna go through like 95% of mostly sad endings😅.