This takes place in an alternate history type world, so no country names we are familiar with, and our MC is out on an artifact dig when they get betrayed. He discovers the ability to relive the past through artifacts with lingering regrets attached to them. By resolving the regrets he can learn the abilities and martial arts of those in the past and bring them into his own body, allowing him to grow stronger.
So we have modern-ish cultivation/martial arts (more martial arts right now at chapter 50) with martial arts being hidden from the general public. The MC has a cheat to be able to gain more knowledge of martial arts that may have been lost in history.
And how is it? I'm having a good time. There are some mysteries in the background (What are shadow demons for one...), the MC is decently ruthless, but not uncaring, and the focus on lingering regrets means that there is an emotional aspect to the story where they have to think about the feelings of the different characters and how to react to overcome those regrets.
Right now I would say 8/10. Definitely a strong beginning, and I am excited to see where it goes.