James, Lorelei. Mastered series.

"Former small-town girl Amery Hardwick is living her dream as a graphic designer in Denver, Colorado. She's focused on building her business, which leaves little time for dating--not that she needs a romantic entanglement to fulfill her. When her friend signs up for a self-defense class as part of her recovery after an attack, Amery joins her for support. That's where she meets him. Ronin Black, owner of the dojo, is so drawn to Amery that he takes over her training--and, in private, her body. A sensei master-artist in erotic bondage, Ronin pushes Amery's sexual boundaries from the start, and with each new, sensation-filled twist of his rope, Amery becomes addicted to the pleasure and to him. But as she willingly gives herself to his sensual domination, Amery begins to sense a secret side to Ronin that he hasn't dared to share--something that makes her question her trust in him, no matter how thrilling her obsession has become"--