Izaya considered dismissing the question altogether. But that would entail that he was afraid.
"I'm afraid I was never 'in love', no."
Shizuo nodded.
"Thought so."
Annoyance seethed in contact with Shizuo's matter of fact response.
"Unless I am lying."
"You're not."
"Oh really. Do enlighten me as to how you reach that conclusion."
"It was kinda obvious but I wanted to hear it from you."
"For all you know I am absolutely head over heels with some girl and am ever so passionate about her."
"If you actually were you wouldn't make fun of it."
Izaya laced his hands behind his head.
"Perhaps. At any rate, 'love' is a mere byproduct of our evolutionary history. Sexual drive promotes the propagation of the species and civilization adds a veneer under the guise of 'love'. Social cohesion between kin and later larger groups also benefit from the 'love' notion."
"Sounds like you have it all figured out."
"I am just an educated individual. Should I forward you some reading material on the subject?"
A snickering bite just underneath his words. Izaya regained territory. Looking down at Shizuo from the vantage point of well-articulated knowledge.
"I'll skip."
Izaya made a clicking noise with his noise.
"Speaking of which, shouldn't you be taking notes? I seem to remember that your memory was not particularly impressive at school."
Izaya's grades were always at the top and Shizuo's dragged at the bottom, they were the extremes between which gradients developed.
"No need for that. And all your fancy talking wasn't needed either. The air quoting pretty expressed what you meant much better."
Izaya's eyes became slits. Then he relaxed into a shrug.
"Or it could be that you just didn't understand a word of it."
Shizuo seemed to consider this. Izaya beamed, afloat in triumph.
"If I'm an idiot why don't you break it down for me? Why go throwing your smart talk at me like that, when you know I won't get it?"
A single eyebrow twitched as a snappy remark occurred to Izaya only to be discarded.
"My, my, 'idiot' is such a harsh term with such a pejorative connotation. I have not said that you were an idiot."
"You don't have to say it. Just like you don't say that water is wet. Too obvious to even bother. You think I'm about as close to mentally retarded as it gets."
Despite his resolve Izaya had to repress inch his way out of the sofa and then out the door. Shizuo might attack at any point. Izaya took a very deep breath.
"In my defense I tend to think that of most people."
Shizuo nodded as if this too was nothing new.
"You don't have to worry about me hitting you."
"I am ever so thankful for your kindness, Heiwajima-san."
Shizuo ignored the pointed sarcasm together.
"Do you keep a file on me?"
"Job related so I won't answer."
"That means 'yes'."
Izaya recoiled into himself by becoming perfectly still. It occurred to him that he had not so much overestimated as underestimated his opponent. And he was all too aware how deadly a mistake that could be.
"My, look at the time. I'm afraid it's getting rather late so I must ask you to call it a night."
Izaya hoped that Shizuo did not have further questions but he thought it unlikely.
"Alright. I'll call you tomorrow."
"No can do. I have important business to attend to tomorrow."
"Saturday, then."
Izaya wanted to call out the entire thing altogether. It was madness. But admitting that it at all affected him was already too grave a loss.
"I'll see what can arrange in my schedule."

Izaya had no actual need for personal files on his object of study. His memory was prodigious and more than capable of keeping track of the minutest details about those people unfortunate enough to capture his interest. But it was a world of fun to turn to the neat folders on his computer and go over accurate descriptions that he could compare at length. He tended to do so in the dead hours that preceded dawn, humming some tune or other, and amusing himself at finding small connections in between the most disparate of individuals: say, that Yagiri Namie just so happened to like the same soda flavor as Ryugamine Mikado. And of course there was one such file dedicated to Heiwajima Shizuo.
He now accessed it with a double click.