Forbidden love with the mafia king

A soul gripper has to catch a soul which escaped his claws but needed a human body.

He transmigrated into the body of a dreaded mafia king who was reported dead.

This soul gripper wasn't meant to meddle in human affairs but only cause death wherever he appears. His time was limited on earth and to worsen it, he lost his ability. How would he capture the soul?

She had the abilities to see ghost inside the body of a human, trained to disperse them, she hunts them secretly while saving lives.

Sadly, she got rejected by her groom a night to her wedding and intended to commit suicide but was saved by a man in dark wears and had a one night stand with him!

Forgetting such night actually existed, she lived her daily life. However, she accidentally crosses path again with the man in dark wears who suddenly claims she was his and needed her help!

Who could this missing soul be?

How long would he last as a human when he's declared wanted in the underworld?

Would she aid a desperate soul gripper who brings about death?

Why did he save her?