guys, is this a sequel? why is it 2? is there something i should read first?

You could call it a sequel indeed, but the MC and most involved characters are different... some are still related tho (mr. Bu is cousin with mr. Yan), and the 'mystery' case that is the focus of the story is also different.
the prequel is titled Poyun in mangago... or just breaking through the cloud, as the novel.

thank you so much <3