I believe the series is getting some undeserved hate right now.
A lot of people complain that Tarou is indecisive, but I don't think that's true. If Ibusuki had never come back, or if he couldn't see love zombies, he would have definitely ended up with Ebino. If Ibusuki came back as a girl, even if he could see love zombies, Tarou would have ended up with her. However, since Ibusuki could see love zombies, she changed to a man so no one could create first love zombies based on her. Do you blame her? Of course not, especially if you see her father. Now, this creates the main issue of the series, because both of them can see love zombies, and while Ibusuki does she has to live as a man, and as long as this happens they can't get rid of Eve by fulfilling their love.
Now, Tarou probably loves Eve but I refuse to believe it's romantically, I think it comes from her being his creation. It has been show that Tarou is incredibly capable, his energy saving schtick is mostly bullshit, but his main pitfall is his great sense of responsibility. He feels responsible of creating Eve, of Ibusuki being able to see love zombies (so she cannot live as a woman), and even feels bad that he has some feelings for Ebino while Eve exists.
The ending is pretty straightforward. As long as Ibusuki can stop seeing love zombies, she can go back to be a girl, which in turn will make Eve go inside her and sparkle, making them able to fulfill their love, and in the omake we will probably have a timeskip where they have a daughter called Eve (probably not but if we go by tropes I'm sure this will happen). Another way is that Ririto just stops seeing love zombies after Eve fuses with her. Any other ending right now is literally impossible, since this is what the author has been setting up for pretty much the last half of the manga -the painting, the snowglobe, Eve's wish- and if this is not the ending I'll eat a shoe. Why didn't this happen earlier? Tarou and Ririto hated each other when she arrived, and by the time they didn't Eve had become a whole person to them, pretty much a friend. The middle of the series was definitely very slow, and not much happened, but in the end it did set up for the current situation. Why doesn't Tarou end up with Ebino? Because he loves Ririto and Eve and 2>1