When the person I used to admire, turned out to be a Yandere!

The twist that FMC was actually a regressor was nice and did a great job of explaining her obsession with MMC. But that’s also the main issue in that it never feels like she actually satisfactorily suffers enough to redeem her enough for readers to get behind her as a good heroine. To say she was terrible to MMC in her first life would be an understatement.
The things she did were crueler than I’ve ever seen with a lot of cheating female characters I’ve seen in other BSS/NTR works. The fact that she still didn’t sleep with anyone else in her first life isn’t enough to mitigate that. I actually don’t mind and even like stories where female characters like this get redeemed/reconcile with the main character or even become heroines again, but the key to making that work is that there has to be a bit of “zama”, there has to be some amount of anguish and suffering these kinds of characters have to go through before they’re rehabilitated enough to become sympathetic in the readers’ eyes.
But there’s never enough focus on the zama for Emiko (Fmc). There’s hints of it with the mention of her mental problems and anti-depressants in her 2nd life but those remain only in being mentioned rarely in passing (in fact, I think there’s only 2-3 times it actually comes up.) And there was a very good opportunity when Haruki (Mmc) gained memories of the original timeline to see Emiko actually have to work to make up for what she did in her 1st life. But in the end, Haruki basically got over it too easily like a simp.
Looking at the story, the real main character is Emiko and she basically got everything she wanted handed to her on a platter. She basically treated Haruki like absolute shit the first go around and only realized she loved him after he died and then she got a 2nd shot to get with him and got what she wanted without much difficulty. I actually can’t remember if she actually ever even apologized to Haruki.
Related to how easy it was for Emiko is how much of a simp Haruki is for her. It’s easy to understand at the beginning of the story when as far as he knows she’s the rich ultra-gorgeous oneesan model who’s head-over-heels for him (but even then, he still should have had more suspicion towards her), but there’s never any satisfying explanation for why Haruki still clung to Emiko, in his first life after all the cruel things she did to him and then again in the 2nd life when he gains the memories. Emiko is so selfish and cruel in the 1st life that it’s hard to see why Haruki would remain so attached to her. We don’t really see much of whatever good side or bond the built initially to explain it. There’s a little bit of hope when he asks Emiko to break up with him after he gains memories of his first life and understandably feels hurt and betrayed. But that’s short-lived when Emiko just wags her tails and make puppy eyes to make him give in and come running back to her. It becomes hard to relate to him when he doesn’t have the normal reactions a person would have in that situation and a convincing reason for his actions.
So those are the two main problems with the story. It’s obvious by the author’s notes that he just wanted to focus on the fluffy romance stuff so it’s probably why he just tried to skip past those pain points but the fact that they aren’t satisfactorily addressed makes it hard to get into the fluffy slice of life scenes. And it makes all the drama introduced seem pointless when the biggest elephant in the room which should be the source of most of the drama gets ignored. In particular, the whole reveal about Haruki’s father being a notorious terrorist was an ass-pull out of nowhere and a real soap opera moment that seemed completely unnecessary.
It seems like what’s disappointing is that the setup seems great for a redemption/reconciliation type of romance but ends up wasted because the author wanted to tell a completely different story where this setup was completely unnecessary and in fact hindered it.
Lastly, there are some loose ends that don’t get addressed. Biggest one is “what was in the box?” It’s basically the smoking gun throughout the whole story. What was in it that made Emiko commit suicide? And why did Haruki ask for it back at the end? Was it supposed to be the same box as the one with the ring Haruki gives to Emiko at the end? That would make sense but the way it’s written in the very last chapter makes it seem like it’s a different box and is gonna be revealed later.