Reincarnation dark romance

Read this around 2023-2024. Best friends (scientists) and one’s wife dies. The widower becomes obsessed with finding out how to find the reincarnation of his wife. Friend finds out that the widower has been killing people in pursuit of his goal- they fight both end up dying.

Years later widower’s son takes up his father’s research. Ends up falling for a guy only to find out that he’s the reincarnation of the Father’s best friend who he had killed.