First off, the relationship between the main character and Nora was so sudden. It's just in one moment, he's all friendly and happy with Gosho along with his family, then he suddenly decides it's better to run off and leave with Nora after one kiss/feeding.
The main character then gets captured and experimented on, thought that'd be interesting, only for a ten year time-skip to happen immediately after. Unexpected, but no biggie. As long as there's obvious effects from the ten year imprisonment on the main character. Yet, nothing. Both Nora and Saku were literally torn apart, yet the main character is just fine. No trauma, no obvious wounds/scars, he just wakes up and escapes.
With help from the same person that tried to kill him multiple times, Saku. Once again, another plot point that was ruined. Clearly had a backstory with Nora, never explained. It also isn't explained why he wants to kill the main character in the first place either. Or why he saved the main character. No good explanation, just some "talking to you made me feel human again" crap, despite only having negative and/or rushed interactions with the main character.
And Nora herself, for such a important character (or something), she had one chapter explaining her backstory... with no words. Are we supposed to draw our own conclusions or something? And after that, both the main character and Nora wake up in a cave somewhere in hobo rags, just to walk off into the sunset together, with either no conclusions or unsatisfying ones to a lot of previously interesting plot points like what the company was doing to vampires, Saku's existence in its entirety, Yuki's transformation and subsequent kidnapping, and the question of why, just why the main character seemingly cares so much about someone that has literally only ever made his life harder, + more.