While I do understand why people hate the MC's attitude (I felt the same at first), I think his behaviour is not entirely abnormal...
The guy reincarnated into a game he wrote every single line of dialogue of. While he has almost no clue about the RPG aspect of the game, he knows better than anyone else the "dating sim" part of it. When suddenly he is sent there and asked to either defeat the final boss or conquer the three heroines, it's obvious he will try his best to get back to his original world as soon as possible by conquering the heroines with a perfect "playthrough". And, normally he should have been able to do so easily, but it turns out his knowledge is not enough because, during the process of turning the game into a real world, every plot hole has been filled with content he doesn't know about, which makes the already difficult "conquest" even more difficult (basically impossible).
Also, the "real" heroines are not as likeable as their game counterpart, not only because of the changes but also because, while you might like a possessive character, you won't necessary like a possessive girlfriend (especially since not being found out cheating is necessary for you to return to your world). This helps him avoid getting too emotionally involved.
And there's also the fact that, until he decides to confess to one of the heroines (and thus, conclude the current playthrough), he can't know their affection level. This would make anyone go crazy since you'll go back to the starting point time after time if the affection level is not high enough when you finally confess.
Spoiler
Anyway, it turns out the MC is actually deceiving himself in order to fulfill his mission. It's especially true with Undecided; he tries to act like an as$hole and treat her like an object, but when (following his orders) she actually treats herself as disposable, he instantly becomes desperate.
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Anyway, the story is not that bad but still far from being perfect.
And if there is something I really didn't like about it it's the second part.
Spoiler
The author used one of the worst combo for me: MC disappears > people think he's dead > time skip > return. Basically, the author skipped through the whole process of making the heroines change and accept the harem situation. Since the guy was dead, they learned to work together to share their pain and achieve what he couldn't do. And then, they are too happy to see him back to actually try and make him unhappy again.
Also, at this point, any girl who is in love with the MC more or less adds herself to the harem naturally, without any real development.
Basically, it feels rushed. The author had the decency to end the story, but it seems to me that he/she backed himself/herself into a corner and just wanted to end it as soon as possible, forcing every development he/she had in mind into a few chapters.
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In conclusion, I liked it enough (Undecided is very funny) and still want to read the remaining chapters, but I don't particularly recommend choosing this one if you have to choose only one series to read.
