All Might and the rest of the class were in a secure room surrounded by screens and monitors.
"Pay attention!" The Number One Hero said to them all with his usual enthusiasm. "This is an exercise both for them and you! Young Brando and Valentine will have five minutes to prepare and get into a villainous mindset! Then Young Midoriya and Bakugo will go inside and the trial will truly begin! Observe them closely, and plan out your own strategies!"
His students all locked their eyes on the screens.
Brando looked at the weapon they were supposed to keep their enemies away from. One touch and they lost. He wouldn't allow that happen.
Valentine spoke up. "So you can change and move fast. What else?"
Brando looked at her. "Claw through muscle, and bone if I'm fast enough, and change other things too, via touch, so long as they're alive. My senses, save for sight, also get an upgrade. What about you? What exactly can you do?"
"My range is limited to roughly two meters," Valentine answered. "But that won't be an issue. All I need is to put our little Heroes between two large objects, and we win."
Brando found that unlikely. "How do you figure that?"
"Because therein lies the true power of D4C. Wait here and get ready, just in case."
Brando raised an eyebrow. "You're going to go after them?"
"Of course. Narrow hallways make it easy for me to appear and disappear if need be. Your talent will be more suited to stopping them on the off chance they get past me." Valentine walked over to the wall. "I wonder, could I borrow you for a moment?"
"To do what?"
"Just come over here."
Brando looked at her... and shrugged. He walked to her. "Now what?"
She grabbed his shoulders and guided him towards her.
Is she going to kiss me?! Brando didn't know what to do.
Then, to his shock, she began to melt into the wall.
"I'll keep you posted," she said before she left completely.
"What the hell?" His reaction was shared among his classmates.
"She just vanished!"
"Did she come out the other side?!"
"Kacchan, we really should think of a plan," Izuku said as he and his partner observed a small layout of the building the two of them were about to infiltrate, intending to memorize it.
"No shit, Deku." Bakugo growled and crumbled up his piece of paper. "Don't think you'll be of any use to me besides being a meat shield. While the blondies crush you, I'll blow both of them to hell."
The greenette didn't like the sound of that plan as they climbed through a window. "But we can't just charge in! Diego can rip us to shreds!" His habit of muttering soon took over. "Then again, so long as we don't get too close..."
Bakugo began to grind his teeth as he led them on deeper into the enemy territory. "Deku. Shut. The. Fuck. Up."
The pure contempt snapped Midoriya out of his daze and he followed in silence. Kacchan... the feeling between us is mutual. I hate you. Loathe you. But... I also have to admit I admire you too. Your ambition is limitless. I cannot help but applaud just how you never give up. And yet... a small part of me wants to see... He shook the thought from his mind. Maybe I've been spending too much time around DIO-san.
On and on they trekked, checking corners and making full turns when coming to a new hallway.
While Bakugo was as steel as ever, Midoriya began to feel dread leak into him. Diego can sniff us out like a bloodhound and bury his fangs in us before we could blink!
Soon, the unlikely duo came to a door. One of which wasn't on the blueprint they had studied. Bakugo smirked at the obvious trap and began to lift his arm up, preparing to blow it away. "Your Brit friend is just as stupid as you are, Deku."
Just as he willed his palms to ignite, the door fell down on him, making him fall to the floor. On it was not who Midoriya had been expecting.
"Dojyaaa~n!" Valentine was crouching on the door like she was a house pet with her Stand levitating above her. "All gone!"
All gone? Midoriya repeated mentally. It was then he realized the door was flat on the ground. Had she crushed Kacchan to being as thick as a sheet of paper?!
Valentine climbed off the door, and D4C brought it up to rest on its side. Midoriya saw that his bully wasn't flattened. He was completely gone.
"Wha- wha- wha-" He made his mind race, trying to figure out what had happened. Valentine would not have killed him with All Might watching, right? Her Stand must have some sort of warping power. I can't let her get close to me!
Back in the observation room, one of the smarter students began making her own mind race. Wait... she crawled under a car and vanished... and now she used the disappearing act on Bakugo by putting him between the door and floor... but she emerged out of Midoriya's arm?
While she was being deductive, her peers were awestruck.
"She just took one of our class' heavy hitters out in under a second!"
"But where did he go?!"
"Did she... kill him?"
"Well now, that wasn't flashy at all."
Yaoyorozu spoke up. "I think I might have an idea on what her and D4C's power is. She can make things vanish by placing them between two objects."
All Might nodded approvingly. "Correct, Young Yaoyorozu! But that's only part of it!"
"Is that why you aren't stopping this?" Johnny asked blandly. "Because you know he isn't dead?"
"Also correct, Young Joestar!"
Back with the action, Valentine gave a smile that in no way made Izuku feel at ease. "Just hold still, and I'll make this quick. No need for pain."
Midoriya wracked for an idea. Okay, getting close is a bad idea, she'll just make me disappear too. I have to take her out quickly! If she goes down, her Stand goes with her!
Her Stand closed the gap between him and its User. He tried to dodge but D4C proved to be fast. The long-eared manifestation landed a punch to his head with such force his hood ripped and his cranium collided with the metal wall.
President Valentine's sucessor laughed. "This is too easy!"
Midoriya saw his surroundings twirl and lose their sharpness, but he forced his thoughts to remain focused. I can't rely on speed to deal with her. I'll break my legs! There has to be something I can do without making my body useless! Wait... the Sludge Villain! All Might's punch left a shockwave after he made the blow!
Valentine raised an eyebrow as her opponent pressed the nail of his right index finger into the thumb of the same hand. "Snapping your-" The next thing she knew was a force of wind comparable to a hurricane. It quickly had her airborne, and, like her victim before her, she collided into the wall far behind her at such velocity that it left an imprint of her body. Seemingly knocked out, or at least dazed, she went limp and fell out of her outline to the floor.
"Sorry," Midoriya said as he picked himself up. His mother had raised him right, and hitting a woman was never okay unless she was a Villain. Realizing just what Valentine was supposed to be, he mentally reprimanded himself. He then felt the wave of pain as a result of breaking his finger. A necessary sacrifice to take out such a dangerous opponent. He peeled off a decent amount of the Capture Tape provided to him before the exercise and bound her wrists and ankles together, eliminating her from the fight. As he forced the ache out of his thoughts, he carried on alone. After making sure his other foe was not hiding on the stairwell taking him upwards, Izuku tried using the wireless communicator currently in his ear to contact his teammate. "Kacchan? Kacchan, can you hear me?" Only static greeted him. Taking in a deep breath, he continued on alone.
A few levels up and several minutes of sheer paranoia later, Midoriya was being even more cautious than before. There's no way Diego didn't hear that scuffle earlier. And since All Might hasn't declared a winner, it's obvious the trial is still on.
Coming to another doorway, out of the corner of his eye he saw a flash of green. He pressed himself into the wall next to the entrance of where Brando had to be. Now what do I do?! I just have to touch the missile to win, but as soon as I set foot in his line of sight, I'm done for!
As he wracked his mind for ideas, a noise emitted from the room. "Wryyy..." It was like a whisper. The softness was instantly replaced by something far worse. A sort of screeching came from the other side of the wall. Izuku remembered how Diego had first demonstrated Scary Monsters all those months ago.
He knows I'm here... so why isn't he- Midoriya could not even finish his thought. Out of the doorway came Diego's tail, whipping him like a circus animal. The impact knocked him along the wall.
"Well well well. If it isn't the Hero," Diego said as his foe shook his head fervently. He stepped through the doorway. Clearly, he was enjoying the role of the Villain. He noticed the dark, bruised finger on his friend. Perhaps Valentine got a hit on him. "Get up, Hero! I want to see your eyes get taken over by despair!"
Midoriya did indeed begin the struggle of returning to his feet. Maybe I could run away, come up with a plan? No, the timer has to be nearly up, and he would just see me coming... I have to finish this here and now!
He remembered the Capture Tape in his pocket. He slowly moved his arm towards it.
"You think I can't see you right now, because of Scary Monsters?" Brando cackled. "There's this thing called 'object permanence.'" He grabbed Deku by the shoulder while his free hand's fingers spread out. "The winner is me!"
Midoriya chose to capitalize on the moment of his boasting. With Brando's guard down, Izuku quickly turned on his heels and wrapped some of the capture tape around the wrist that had been on his shoulder. Before Brando could comprehend what just happened, his opponent ducked under his arm, bringing his ensnared hand with him, forcing it onto Diego's side. Finally, Brando caught on to what Izuku's intentions were, and his free hand clawed at the tape, cutting it to ribbons. "You irritating pl-"
His insult would never be finished. A mighty gust of wind blew him off his feet, sending him backwards like a tossed rock into the metal paneling far behind him, all while Midoriya winced at yet another shattered finger.
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Seeing the slaughter unfold before him, his peers, and their legendary teacher, Gyro nudged his closest friend in the ribs. "Ehi, Johnny. You know Dio better than anybody. What's gonna happen now?"
Johnny's veneer remained the same as several pairs of eyes turned to him for a moment. "If it weren't for the cameras, Dio might have gnawed your little friend's arm off." His words were so dry and deadpan, nobody could tell if he was serious or just joking. "Anybody else wondering where Valentine went?"
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"I was hoping not to play this card so soon, but I can't show weakness to them so soon!" Siri was desperate.
The one she hoped would help her considered. "I fail to see what's in it for me."
"Um... the knowledge that you are the go-to for me in my hours of need?"
"Not good enough."
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The timer was dwindling down, Izuku had to lay his hands on that fake missile and he had to do it now. Running like the Devil was on his tail, he made a beeline for the objective, his lungs aflame and adrenaline pumping... only to run out of the doorway. Seeing that he was about to collide with the wall, he stopped and skidded to a halt, all the while bewildered.
What?! How did I...
"You aren't going crazy, in case you were wondering," said a certain somebody behind him. He knew the voice well at that point, and he knew it was most unlikely the speaker would have gotten to him so quickly, given the earlier attack.
He turned around. Standing between him was a ruffled Siri Valentine and...
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Étoiles au-dessus!" Aoyama exclaimed as he and all the rest spectated.
Even Todoroki's stoicism briefly cracked in the form of raised eyebrows. "Two of them?"
"But that's impossible! Right?" Kirishima was not sure what to believe at the moment. One of the screens showed Valentine and Brando facing down Midoriya, while another showed... Brando barely responsive on the floor.
"Is that the other part of her Stand's power?" Hagakure wondered aloud. "She can make copies of things?"
"Not exactly, Young Hagakure," verified All Might.
Yaoyorozu spoke next. "At least we can tell them apart." She pointed towards the newcomer's head on the screen. "The 'D' pinned to his helmet is backwards."
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How is Diego there?! He didn't get past me, he would have clawed me in the back. Midoriya's mind was split like timber. Half wanted to figure out how his friend (currently foe) had all but teleported before him. And the other half desperately tried to come up with a tactic to deal with two Stand Users.
"Got you frozen, huh?" Diego smirked. Behind him, a newcomer appeared. It had to be a Stand. It was predominantly yellow, with a mask-helmet covering its face above its nose, with diving cylinders on its back. One clock-esque protrusion was on each of its hands, just below the knuckles, and capital D's were on its knees like protective pads.
Midoriya brought up his fists, ready for a fight. Either Diego has been hiding his actual Stand manifestation from us... or this is an imposter.
Diego or not, whoever the blonde jockey was pulled a rather large knife out of his boot.
"Hey! I said stop him, not hurt him!" Siri shouted.
"While they aren't mutually exclusive, this calls for both."
It happened like lightning. One moment, Brando was in front of the missile.
The next, he was breathing the same air as Midoriya.
On reflex, Izuku took a swing at him... only for his fist to hit the metal on the wall, making him wince as he again tried to find logic in the madness. He was certainly not anywhere near the barrier, and Diego had been right in front of him.
That, and his arm was bleeding. The fabric of his costume and his forearm flesh was sliced straight and narrow... with a knife. Again, maybe he was indeed dealing with a rejuvenated Diego; he had seen those arms move like blurs before.
"I didn't have much time to plan," Brando said as crimson ichor dripped off his blade. "But you seem simple enough."
"We just need to run out the clock," Valentine sternly said.
"Yes, I'll keep that in mind, Valentine. Now then." His Stand reared its arm back... and again, the duo were gone from Midoriya's sight. He did not know where they went. But he was fully aware of two other things: his gut had been punched. And his hood was in tatters.
Maybe this wasn't such a good idea... Valentine mused as she watched her secret weapon outmaneuvere Deku again, having his yellow Stand strike him over and over again. Twas the sad fact of Stands versus Quirks. Stands were like radio and television; interaction was strictly a one-way street.
Brando kept his distance, letting his Stand do the damage. His prey swung his arms but they passed through THE WORLD like smoke. An opening would soon present itself. The manifestation of his will grabbed Midoriya by the neck and pinned him to the ground. Diego smirked as the greenette fruitlessly tried to get the grip on him to stop, circling him like a shark.
"I'm going to carve my name into your face," he stated, brandishing his knife and preparing to crouch down.
"Oh, you are most certainly are not!" Siri declared. Sure, she was supposed to be the Villain in this exercise, but that was going too far.
Before anybody could do anything more, a buzzer roared to life, giving Brando a slight headache.
All Might's voice, is both the speakers and the listening devices in the students' ears, declared, "Time's up! The winners... are the Villain Team!"
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Closing Notes: While it is true that D4C requires two objects to send something away, I find that Funny Valentine coming out of Diego Brando's back in Steel Ball Run canon makes it evident that only one object is needed for Valentine to return to the base dimension.