This story has the making of something epic since the characters in the manga grow up and experiences various hardships, etc. And a lot of the characters are likable.. But at the same time, all their situations are too unbelievable.
The situation between Nana and Yano happened in junior high when they were 13/14. They had such an 'adult' relationship it was hard to believe that Yano would have settled for the super innocent and fluffy romance he had with Nana-chan, when they're both now around 16 with raging hormones and all! It would be more believable if all the characters were a bit older and the first events happened in high school and Yano met Nana-chan in college and then from there on.
Secondly, what was up with Yuri? There's really nothing in her history to make her grow into such a twisted person that she would use her sister's death and then her mother's in the way that she did in the manga. She was never bullied as a child. Her whole family loved and cared for her. In school, all people did was call her cold for ignoring them, which she did. Again, no one bullied her. As an adult, even her coworker was super nice to her and actually thought of her as a best friend. Like seriously, no drama whatsoever. Sure, her sister was the prettier one but she was also known to be extremely dumb. I also don't understand her obsession with Yano and the whole Yuri/Yano thing was the hardest to understand and it took over most of the manga. I don't understand her obsession with him for it to last over ten years. I also don't understand why Yano even bothered with her the very first time because he moved on from Nana's death pretty quickly and fell very deeply in love with Nana-chan.
Just. The manga could be so much MORE but wasn't able to grasp it. Like the author tried to make it deeper but stopped and then certain relationships don't seem justified to behave the way they did.
IDK