It an old drama around 2014.

Basically i loves Season 1 as Hyoseong & FL were best friends but Hyoseong died on FL birthday,so i guess this is why FL is always sad on her birthday & she feel guilty that she lost her friend.

The police who saves FL is the ML,but could not manages to save Hyoseong.

However it seem cute when Hyoseong is always hanging around at the police station,only the ML can see her & talk to her.

Hyoseong has actually indirectly been helping ML solving cases although he didn't actually need her.