Yay, it's over. I'm actually glad it's over, not because I'm glad it happened, but because now I can move on!
Of course with the series ending this soon it would be rushed, but gee, the entire story was rushed from start to finish! A marriage proposal before they start dating as high schoolers? A marriage ending when we don't even see them being good matches for each other?
The main issue with this story is that the author wants to reach the endgame before going through the actual game, he's just speedrunning the plot. I'm sure in his mind the characters have these amazing moments and chemistry that make them the perfect match for each other, but since we never played that game and are just watching the protagonist go out of bounds for that sweet world record, it just seems like a bunch of disjointed moments that don't stick with the audience.
This manga needed more chapters, not because it ended before it should have, but because the story didn't even begin properly! Spend time fleshing out your characters, their dynamics and the consequences of their actions and how that changes their worldview! The girls slightly trembling in front of the protagonist is not a substitute for a proper story!