thats basically what a unreliable narrator is. He is so unreliable that he cant tell you any information about the main plot. He doesn’t even remember his own name. He forgets stuff and thats what makes him an unreliable narrator. Also the relationship going too fast, its because its not following according to script. Thats also why the main plot has barely any information. The mc cant give as much information because plot has strayed. While it might just be bad writing or narrating, i like to think its because he is slowly losing himself due to the plot straying and him forgetting his past self. Also i do agree they got down and dirty way too fast HAHAHAHAHA.
Some tag spoilers though: this book will contain angst and from the reviews of the novel(since the novel is unaccessible) looks to be a hopeful ending instead of happy ending.Not sure if the manhwa will differ.
ACTUAL SPOILERS:
apparently there will be a rape scene. Im not sure by who and to who but the reviews stated “the rape was not needed” also not sure if it has happened because i skimmed through the smut.

Became boring and confusing. The sex scenes are really not necessary because the story barely progressed and according to the novel, it gets more boring with empty scenes and lame mundane-like scenarios rather than focusing on the transmigration plot. The uke also ticks me off with how contradictory and how fast everything is happening. Felt like wasted my time reading this. There’s also a rape scene so nahhh