I honestly don't get people who whine that author is a coward for not choosing the only main heroine. You know what, tell that to Negi, who just threw our way pre-planned ending while forgetting to write the substance of said ending. With what he did, Tsutsui can be anyone but a coward. Just look at the shitstorm his decision brought.
I prefer to think Tsutsui loved all of his girls so much that he gave every one of them a happy ending. Yeah, maybe he liked
Kirisu's ass some of the girls more than others, maybe he loved them equally just like a certain infamous mangaka. However, the strive to give all of them not only the main prize of Yuigabowl but a truly happy life is something worth admiration. So what if it makes the manga similar to eroge games? Too many times after reading I regretted about those who were left without any ounce of happiness. Tsutsui had enough bravery to say that yes, nothing is certain because future holds infinite possibilities; in that sense it's the most realistic ending. But on the other hand, he's done everything to give each their own share of happineness.
Tl;dr Furuhashi best girl