Keyon had been with Alla for so many years, he had never touched her, not even when their love deepened. He would only kiss her. He felt he should first build a home for her, and only touch her after he had married her in a grand manner. But Alla, his Alla, gave herself to Casiano for him. First, she gave her body, then her heart.
And he, Keyon, was not regretting not having touched her, but felt it was not worth it for her. She had given everything to Casiano, yet he treated her like this. He even forced Alla in front of him, which showed that he didn't regard Alla as a person, but just a tool.
Even if he knew Casiano lost his sanity because of jealousy, anger, and possessiveness, he still felt Casiano wasn't worth it! He misunderstood that he and Alla had slept together, right? Then let him know the truth, let him live in the guilt of misunderstanding Alla for a lifetime.