They are missing some parts that should've been explained well in the story. Instead of explaining it, they started going further and further with the plot. Maybe that's the reason why it started to get boring. It's been so long since Arthur get together with his bestfriend. Is the author letting it cook some moreeeee?
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Spoiler!
If you are talking about Nico, well they are not best friend anymore because Grey killed Cecelia in their past lives. Both arthur and Nico got reincarnated but arthur isn't aware of that, im talking about the boy who got kidnap who wears glasses was actually Nico's reincarnation that will become our antagonist in the future.
I stopped reading this last 2020, waiting for more chapters. Right now as I finished re-reading 'till the last update, I was really disappointed. It was only good at first, then it started to get boring. What the hell happened to the plot. It's like their trying to prolong the story but honestly they're just messing it up Σ(っ°Д °;)っ