It was Kyon.

Over the time Kyon had been a part of the SOS Brigade, he had entered the room to see many a strange sight. Many of those sights involved Haruhi doing something horrible and/or lewd to Miss Asahina. What Kyon saw now, what he never imagined he might see, was the leader of the SOS Brigade literally fingering the official mascot of the group in her vagina. Or, more accurately, Succubus Haruhi fingering Centauress Mikuru. The two girl turned to look at him as he entered, but Haruhi did not stop her sexual **** simply because someone happened to be there to see it. At least, she didn't until he realized his pants were starting to feel tight and he realized seeing these monsterized versions of girls he knew doing...this...together was turning him on, something Haruhi noticed as well.

"I never knew you were into this sort of thing Kyon," Haruhi said as she removed her digit and strode over, her radiant beauty magnified by her newfound succubushood. Kyon didn't bother to resist as she stood on her tiptoes, bringing her face closer to his, and whispered, "Want to join me?" Then she kissed him on the lips, and Kyon found himself kissing back, swapping literal spit. Which was when it occurred to both of them that Monster Girl Virus could affect guys too, and when it did the "Girl" part of the name still held true.