This particular manga is a shining example of why so many authors choose the shitty open-endings/ or already have a girl chosen from the start (usually the first). Everyone here has a particular heroine they like, for whatever reason. So all this has done is made it to where there is no real happy ending because 4 characters + their fans are getting the short end of the stick.
As much as I hate this scenario for those reasons, I can at least give Negi props for choosing to have 1 girl whoever it is, be chosen. Instead of prolonging the story and have a horrible ending where it hints/doesn't get with anyone in fear of the fans trashing the story. Or do what everyone else does, once a girl is chosen (usually the first)have the others fuck off into the abyss after building them up to be a heroine. Hell, even Nisekoi where there was a "winner" still felt like a kick to the groin because even at the end it was some roundabout bullshit where they STILL didn't really "get together".
Still, all this would be resolved if it ended in a harem like Maga-Tsuki. People think that's the easy way out, but except in hentai or an isekai, PLEASE SHOW ME how common a story that is over what I mentioned above.
This manga is incredibly unrealistic, no matter how "realistic" the author attempts to make the characters. Why not just have fun with it, lol.