Lone Wolf by Persephone Black

I’m the perfect solider. Feared. Respected.
And utterly alone.
I don’t need friends. I certainly don’t need a partner. But the Styx Syndicate has paired me up with Sunny Santiago.

She’s everything I’m not—reckless, warm, alive. She laughs during missions, flirts during combat, and treats danger like a dance floor.
I hate her relentless optimism almost as much as I hate how perfectly we work together. Because somehow, despite every attempt to keep her at arm’s length, we’re unstoppable together.
One moment of weakness in the aftermath of a mission changes everything. I know better than to let anyone close—a weapon that cares is a weapon that fails.
But when a high-stakes mission brings Sunny’s tragic past crashing into our present, I’m faced with an impossible choice: remain the emotionless killer I was created to be…
Or risk everything to protect the one person who makes me feel…something again.

Lone Wolf is a Red Rivals story starring one very damaged ice queen who loves her solitude and one very determined (but also damaged) ray of sunshine who has made it her mission to melt the ice. It’s best to read the Red Rivals books in order because there are major SPOILERS for the rest of the series in this book.
This book also contains spoilers for the Colombo Family Duet.