Phantom Mine By Khai Hara

A year and a half ago, everything changed.
My sister, my best friend, was murdered–and it was my fault.
I brought her to London. I dragged her to the club where she was kidnapped. I lost her.
Adriana paid the price for my mistakes.
The guilt and grief have eaten me alive, but I’m done hiding in the shadows of my failures.
Our brother spent eighteen months chasing ghosts, trying to find her body, her killer, only to come up empty handed.
Now it’s my turn.
I won’t be sidelined any longer.
I’m going back to Firenze, the club where it all started, and I’m going to find answers. I’ll turn over every rock, burn every bridge, and make any enemy necessary to get to the truth.
There’s nothing I won’t risk and nothing I won’t do to avenge Adriana.
Not even if it means going head to head with Matteo Leone, the man second in line to become Don of the Italian Mafia.
If he doesn’t get out of my way, I’ll make him.
I didn’t expect to find a kindred soul behind the mask, a soul I’m quickly learning I can’t live without.
There’s only one problem–at least one of the Leones is responsible for Adriana’s murder.
And it might be Matteo.

Phantom Mine is the second book in the London Underworld series. Although it can be read as a standalone, it’s recommended to read Devil Mine first to get a full understanding of the subplots.