Fighting for You — Megan J. Parker

Nikolai has a dark secret. Raised by the head of the Russian mafia, Nikolai has held back his bestial urges through fighting in underground rings. Now, a cold and ruthless killer, he's lost all hope and feelings of love. That is, until he comes face-to-face with the daughter of the Russian mafia… Natasha has a dark secret. And as secrets have a way of doing, it's complicating her hopes at having a normal life. However, when your father's the head of the Russian mafia and your life is in constant danger, normalcy is far from the norm. Only after she comes face-to-face with Nikolai, she discovers that some secrets are worth keeping.