From what I've seen so far, the main love interests are Arden, Franz and Linnaeus. I've seen 4 out of 9 possible endings, so my guess by the ones I've seen is that you have a good and bad ending for each of the love interests, plus 3 that are different (because one of the four I've seen was an ending that had little to do with any of the love interests). There's also a side romance, but I haven't unlocked it yet, so can't report on its contents...