I liked how the plot unfolded throughout and I totally didn't expect the mystery element when the story started (the focus is still on the romance though). I thought two volumes was a good length to tell the story, and even if some things could have been explored more thoroughly (there's some alternating POV, but I would have liked to see more of Mikami's perspective, and Ibuki's aka Soba-kun's life after highschool), to me the conclusion was pretty satisfactory (I was also a bit worried about Mikami's original future husband, lol, glad that got resolved -- in a fun way, I thought).
Mikami can be a bit of a jerk and is still just a kid, but at least he's self aware, lol, and I would have LOVED to see Ibuki get angry at him once in a while instead of constantly apologising for every little thing.
I mean at THE VERY LEAST for outing them as a couple to all sorts of people. What the hell, man?!
That said, I probably also would have thought Ibuki was a stalker if I was in Mikami's shoes, haha.
I don't think it was mentioned just exactly how much time passed since highschool, but since Ibuki finished college and got a job he must be at least 23 when the story starts. And that kind of bugged me throughout. Yes, he's timid by nature and might not be the most capable and independent person in his adult version (this is just an assumption, at least his parents were against their adult son living alone), but he isn't completely socially inept, yet he was acting so much like a naive 16 year old, which was partly endearing, partly annoying; I would have liked to see a bit more rational "hey, I am actually the older and more experienced one here" thinking from him.
The way the got together might have been a little due to the suspension bridge effect, but I did think Mikami genuinely fell for Ibuki in the end. A three page extra showing them a few years down the line would have been nice to complete the picture, but oh well.
A BL with a similar premise (having regrets and getting a do-over in highschool) that I liked more is Anoyo de Omae ni Sukida to Ieru; and for the mystery fans a time travel thriller with gore that's BLish: Kimi ni Nidome no Sayonara wo