So this series is about MC who claims to be the mad scientist of this era and is pretty much a dislikeable guy. The novel explains you why he became the twisted person he is, and unless you're reading this hoping for some self-satisfaction or self-insertion, you have to understand the guy and why he does what he does. One day he sleeps with his childhood friend while just holding hands and the next morning her daughter from the future appears in the same bed, saying she came from the future to fix her family because MC and his childhood friend are divorced in the future. That's basically what volume 1's all about. At best it may be "interesting", but mainly because of the focus in the character's psych and emotions. Plotwise this is just another romcom with a twist where the MC is crazy.
Volume 2 evolves this concept a bit. It remains a romcom but now you see how the plot of future travel starts being more relevant to the story. You get a glimpse of the reasons he and his childhood friend broke up and realize that whatever happened in the future may be more important and dark than what you think.
Volume 3 is where sh*t goes down. Whatever romcom-esque feeling this novel gave you was just a buildup so you'd realize how grave the whole situation is, to the point it even becomes despairful. This is now a drama built on a 2 volume preparation of relationship building and some quamtum science. It's no longer about saving a marriage or making a child happy, or just getting the girl. It's about trying to fix an unfixable broken person and family. And if that doesn't get you pumped up and willing to read this novel then just go ahead and skip it bacause it's only gonna get heavier from now on. The characters are flawed. Even if it is obvious to you and your morals brought by common sense, you'll be forced to understand that when faced with adversity, a person may not able to change, even if its the obvious solution. It gets hard to read to be honest. Not because it's cringy or badly written. On the contrary, its so well written that even if on a personal level you reject what's happening, you gotta understand and just hope things change soon.