Wu Xin: The Monster Killer (2015)

Both dramas feature a male lead with mysterious powers, solving cases.

Im Wu Xin the male lead is immortal, but doesn't know why.

In White Cat Legend the male lead is a cat-person, and also doesn't know why.

Wu Xin focuses somewhat on romance, while WCL focuses more on friendship, and camraderie.

Supernatural/fantasy element during republican era.
Both have male lead that had lived for a long time (immortal). They also tried to help others and vanquish evil spirits.

Same supernatural concept with different side stories between human and spirits.
Male Leads are immortal.

Both are a good mix of romance, comedy, drama, fantasy, and supernatural. The actors are amazing. Ghosts/monsters also always find the heroine, and the hero helps to protect her. Each ghost case imparts some food for thought.

Both are supernatural/fantasy dramas with an immortal male lead who falls in love with a human girl. Both have epic bromances, as well!

- They're both connected of fighthing evil spirits though in wu xin theres no collecting points to become a deity