While Hannibal may occasionally flirt with women, he is very gay, and very attracted to Will Graham. However he makes every effort to keep his relationship with Will strictly platonic, if not professional. He intends to keep his desires hidden, indulging himself with thoughts of Will only when he is in solitude.
Will Graham always just assumed he was straight, (though he's had very few romantic encounters), but the more he gets to know Dr. Hannibal Lecter, the more he begins to doubt himself. He admires his therapist, in a way that has been becoming much more physical as of late. One day, during a session with Dr. Lecter, he thinks to himself that it would only be therapeutic to act on his feelings. So he does.
Hannibal smiled to himself as he looked at the clock and saw that it was 3 minutes to 7. 3 minutes until his session with Will. "You are his therapist," Hannibal reminded himself. At precisely 7:00 the doctor opened the door from his office to the waiting room to find Will stumbling through the main entrance like a [insert simile here].
"Come in, Will," he said. "How are you this evening?" Will snorted a laugh as a reply. "Not well, then? What has been troubling you?" He motioned for Will to sit. "I sense something beyond your usual difficulties, Will." Will sighed as if he were about to visit a place in his mind that he'd rather not.
"I've been struggling with… feelings for someone," He admitted. This came as a bit of a shock to Hannibal, who then scolded himself. Just because the man had social difficulties did not mean that he was incapable of having a relationship.
"Would you like to tell me about that?" Hannibal asked.
"I'd, um, rather not…" But Hannibal's curiosity overpowered his professionalism (for the first time, ever) and he pushed the matter further.
"Perhaps talking about these feelings could relieve some of your stress," he pointed out.
"Do you really think so?"
"It's your hour, Will."
As if he were waiting for those exact words, Will leapt from his seat and a moment later his lips were planted on those of his therapist.
"William," Hannibal breathed. Will's soft lips crushed into his own and Hannibal allowed his lips to part. Will's tongue began to massage his, and he allowed it. He savored it. Hannibal was not usually a man to submit so easily, but he had waited for so long, and the kiss did take him by surprise… But Hannibal was a man who preferred to be in control. He grabbed Will by the shoulders and used his position to gain leverage. Will accepted Hannibal's dominance and they danced in this way for quite some time, fingers knotting in hair, lips exploring their territory. Eventually the two came up for air and saw that Will's session was just about over.
"I will see you next week, Will," Hannibal managed. He went to bed that night with a smile on his face.