#blackwhip

Izuku didn’t know how it happened. One minute he was lost in thought, minding his own business, and the next he was sat with a livid, ensnared Katsuki Katsuki, The Great Explosion Murder God Dynamight, dangling only a few inches in front of him.

Katsuki had stepped into the common room to get a snack when he noticed Izuku sitting on one of the couches, clearly zoned out. I’ll leave him be, Katsuki thought. That was until four spidery black-green tendrils burst forth from the green haired boy, rapidly approaching Katsuki. They snatched each of his limbs and he was promptly flung over to that same couch.

“...Deku.” Katsuki growled, glaring at Izuku upside down.

“Ah! Kacchan!? How did you get here-oh. Oh.”

“Care to explain?”

How could he let Blackwhip get out of control again!? He hadn’t even noticed Kacchan walk into the common room. Though he had been thinking about him, thinking about his muscular physique, how he wanted to put his hands all over him and—

“Deku! Earth to Deku!”

“AH! S-sorry, Kacchan. Um, I-I really don’t know how this happened. Honest! I didn’t even know you were here!”

“Whatever, just let me go already.”

“Right, yes of course.”

He tried. He really did. But no matter how hard he tried, he couldn’t let go.

“Uhh… About that…”

“Don’t tell me.”

“...”

“You don’t know how to release me?”

Izuku nodded, horrified.

“Alright then. Brace yourself.”

Hands tied behind his back, Katsuki set off some small explosions. It was no use.

“You could have at least picked a less humiliating position, you know!” Katsuki exclaimed. “What is this, some kind of shibari!?”

Katsuki hung like a chandelier, his wrists and ankles bound together while the rest of his body dangled freely.

“I-I-I don’t know! I didn’t do it on purpose, I swear! I wasn’t trying to do anything!”

They stared at each other for a moment.

“...What were you thinking about before this happened?” Katsuki asked.

“Uh, w-well I, uhm…”

“Spit it out!”

“I don’t think you want to know!”

“I do if it’s the only way to get me out of this damn thing!”

Deku groaned. Why this, of all things?

“I was thinking about… you…”

“And?”

“Touch—”

“Touching me!?”

“No no, not like that!!” A bright blush spread across Izuku’s face. “I was thinking about t-t-tickling you.” Izuku avoided Katsuki’s burning gaze.

“...Are you serious?”

Izuku squeezed his eyes shut and nodded. The two boys stayed silent for a moment.

“If… If that’s really the only way, then,” Katsuki started, “Can you at least take us to your room first? If anyone else sees me like this, you’re dead.”

“Right.”

Izuku cautiously stood up. Katsuki was brought up with him. Izuku almost wanted to laugh now, having calmed down after realizing Kacchan truly had no say in this. He checked to see if there was anyone in the hallway before racing as fast as he could back to his dorm. Katsuki lightly bounced up and down with every step Izuku took as he trailed behind him.

Thankfully, Izuku managed to evade everyone else on his way back. He quickly shut the door behind them and brought Katsuki over to his bed. He attempted to set him down onto it, but Katsuki ended up hovering a few inches above it instead. Izuku sighed and sat on the bed himself, facing Kacchan once again.

“Just know I’m going to get you back for this, tenfold.”

“I know.”

Katsuki tugged at his binds, testing his mobility. “Little help here?”

Unable to get a handle on his quirk, Izuku unintentionally shifted Katsuki into a classic shibari pose, his wrists and ankles now bound together behind his back. A few more tendrils burst out of Izuku against his will, securing Katsuki further still. They wrapped around Katsuki’s body in a flattering way, accentuating his form.

“Not helping!”

“Agh, I’m sorry, I can’t control it!” Izuku whined.

“Fine! Just, get on with it!”

The tendrils appeared to tighten as Izuku’s nervousness increased. Katsuki noticed this and, not wanting to prolong the situation, said, “Breathe, nerd. You're stressing your quirk out, or some shit.”

“Oh! I-I think you’re right.”

What a fascinating development, Izuku thought. Seems like I really have to go through with this in order to regain control of Blackwhip. It’s not like Izuku had never tickled Katsuki before. They used to have tickle fights all the time as kids. Being insanely ticklish, Izuku always lost. He had never gotten a real chance to test Katsuki’s limits before…

With no other choice, Izuku reached forward and placed his trembling hands on Kacchan’s waist. Katsuki squeezed his eyes shut. Blackwhip buzzed with anticipation. Izuku focused, squeezing up and down Katsuki’s sides experimentally. Katsuki inhaled sharply. Izuku moved towards Katsuki’s abs and, feeling a little more brave, dug all ten fingers in.

“Hrmph!”

Izuku could feel his nerves dying down. “Come on, Kacchan!” If we have to do this, we might as well enjoy it. “Laugh for me!”

“O-over my dead bohody!”

Izuku could feel a carnal desire festering inside of him. I must want this really badly if Blackwhip is spiraling this wildly out of control, he thought. And if this is my one chance to tickle Kacchan to pieces… I’m going to take that chance.

Blackwhip, heeding Izuku’s call from within, sprouted several more luminescent tendrils. Izuku and his new tendrils surged forward. Izuku vibrated his fingers into Kacchan’s rib cage, searching for every little sensitive spot he could remember. Two of the tendrils snaked around each of Katsuki’s legs, wriggling up his pants and tickling his knees and thighs. Two more snuck up his shirt into his armpits. Another two found his ears. The final four targeted his feet: two brushed his arches while the other two slithered in between his toes.

“BAHAHAHAHA FUHUHAHAHAHAHAHA- WHAHAHAHAHAHAT AHAHAHARE YOU- AHAHAHAHAHAHA NOHOHOHOAHAHAHA!”

Oh, he couldn’t handle it. Katsuki had never felt anything like this before. It was maddening, yet somehow… kind of addicting.

“IT FEELS SO WEHEHEIRD! G-GEHET YOUR DAMN QUIRK UNDER CONTROHOHAHAHAHA!”

Izuku’s eyes were glowing green. He had an indescribable look on his face—some mixture of elation and determination. He continued to explore Kacchan’s rib cage, trying to find that one spot just above his upper ribs below his arm-

GAHAHAAAAA! DEHEHEHEHEHEKU! NAHAHAHAHAHAHAT THEHEHEHEHEHEHEHEHERE!!”

Bingo. Katsuki shook his head, it being the only body part he could really move. Blackwhip was still going at its respective targets as Izuku continued to massage those two little spots below Kacchan’s armpits. Katsuki felt as if his mind was turning to mush.

Izuku had never seen Katsuki like this before. He was in some kind of trance, enraptured by Katsuki’s raucous laughter and trembling form. He was enjoying this a little too much.

“P-PLEHEHEHEHEAAAHAHA! STAHAHAHAA!”

Katsuki couldn’t take much more of this. He felt like every single nerve on his body was tingling. He’d never felt this ticklish in his life. How was this even possible!? His position, the mixture of sensations, the look on Deku’s face… It was all too much. He had to do something, anything, to get out of this, but he could barely think. Is this what Deku felt like when he begged for mercy—oh!

“DEHEHEHEHEKU! AHAHAHAHAHAHAHALL MIHAHAHAHIGHT!!”

Their childhood safeword.

“Eeh? Ah!”

Izuku stopped and pulled back immediately after he processed what he had heard. Blackwhip fully retracted seconds later, depositing a dumbfounded Katsuki onto the mattress below.

“Oh, thahank Gohohod…”

“Oh my gosh, Kacchan, are you okay? What happened? I totally blanked out there!”

“I am… I am going to kill you. COME HERE, YOU BASTARD!!!”

“WAAAAHAHAHAHAHAHA! K-KACCHAHAHAHAHAN!?”

Katsuki tackled Izuku, grabbing his flanks and crackling harmless little explosions all over his waist, hips, and thighs.

“You’re not the only one who can use his quirk for tickle torture! How do you like it, huh!?”

“AHAHAHAHAHAI’M SAHAHAHAHAHAHAHARRY!!”