Pairing: Izaya/Kida, Shizuo/Izaya

Prompt: For whatever reason (get creative!~), Kida is compelled to say exactly what's on his mind – EVERYTHING. If he thinks it, he says it, no matter whether or not he wants to. When Izaya finds out, it's a massive turn on for him.

BONUS if, after smut, the "disease" transfers to Izaya and he has to transfer it to someone else.

"I jerked off to online gay porn and that's why I didn't do my homework."
Kida bit his tongue but it was too late. The words were already out and the truth, the dreadful truth, accompanied them. The teacher stared at him without quite knowing what to say. Students were not supposed to be this honest. Fortunately the class took it as Kida being, well, Kida and the teacher was too stunned to actually do anything.
Kida had no idea why he could not manage to lie but so it was and it did more than disturb him, it terrified him to no end. He was about to skip class altogether but Mikado was not one let him do that and caught up with him just as he was about to dash down the stairs.
"Masaomi! Wait up! You shouldn't say those kinds of things, imagine if the teacher believed you. And everyone else, too."
Kida bit his tongue anew but it was no use. He formed a banter reply in his mind but opened his mouth to say,
"But that's why I didn't do the homework, I found this hot video with a bottom that looks just like Izaya and it was way too hot for me to resist so I stayed up all night playing it on repeat."
Mikado blinked in perfect shock then laughed shakily.
"You have got to stop making fun of stuff all the time, Masaomi."
"And one of the guys looked a bit like you too but you're not my type. Izaya is way hotter, I mean you're not too bad yourself but it's not the same. I'd let you suck me but not do me."
This was getting worse by the second. And it got worse yet. At least up to this point Mikado hadn't taken him seriously.
"Hey, what do you mean...? How can you like Izaya better..."
Heaven be thanked, Kida reached the gate and ran out before Mikado had a chance of following. Kida ran and ran until he ran into someone.
"Masaomi? Hi there, how are you doing? Shouldn't you be at school this time of day?"
Kida did not know that his luck could possibly be this bad. With so many people in Tokyo why did he have to bump into Izaya, it was beyond unlucky.
"I had to leave because I can't tell a lie."
Most would have laughed it off as a joke and Kida had some hopes that Izaya would do the same. But it was not to be.
"Eh? Really now? Okay, let's try it. Is there anything about you that you're afraid I'd find out about?"
Kida bit his tongue even harder now. He prepared some innocuous reply. To no avail.
"I took one of your boxers from the underwear drawer and rubbed it against my dick as I jerked off to thoughts of you."
Izaya clapped and proceeded to skip around him.
"So it is true, you can't lie! It is extraordinary! I wonder why! But more importantly, I wonder how much fun I can have because of this."
Kida could have wept. Maybe this was an awful nightmare and he would wake up next to the stolen boxers. Kida made a vow never to use said boxers ever again. Izaya patted his head as if he was a pet.
"There, there, no need to look so upset. Tell me, what do you think of me?"
"I think you're so hot that I want you to fuck me, doesn't matter where."
Izaya whistled, his eyebrows arching slightly. This must be fate.
"Masaomi, why didn't you tell me this before?"
"Because you'd troll me forever and tell everyone."
"Tsk, I wouldn't say everyone. But enough talk, let's get down to business."

At least Izaya did not simply drag him to some back alley and had his way with him. Instead he took Kida to his posh apartment where he escorted him to the bedroom.
"Isn't this absolutely great?"
"Not really but there's nothing I can do."
"Heh, quite."
Kida was almost relieved when Izaya kissed him fully on the mouth, at least that way he could not possibly end up saying the most compromising of things. His relief was short lived as Izaya lost no time pushing him flat in bed and making him moan by licking and biting an ear.
"Is this your first time doing this kind of thing?"
"Yes and down deep I always wanted to get it on with you."
"So you're gay?"
"I'm just gay for you."
Izaya was in the process of unpeeling clothes out of him but he stopped to laugh now.
"You really can't lie!"