When the boy thought that he had hit his natural peak of martial arts talent, already sure that he wouldn't ever go beyond what he could do, like any of those real "big" martial artists that could win local and regional tournaments. The young boy hadn't even participated in any of them, neither had he sparred, Quirkless, any sort of martial artist. Kouta just figured that he wouldn't be able to really give a proper fight. Instead, he developed the things he could do with his quirk, choosing to forgo the mastery he was "sure" he'd never achieve and, instead, have so much variety options that he could overcome any sort of style weakness by shifting entirely.

Mixed is a thing, but, with his quirk, he was the All-Trade sort of person.

"With my Cape-Weapons, I can do a lot of stuff. I just need to learn at least a few bit more than juts the basics with whatever weapons I try. 
Like.. to become capable enough of using it all? 
I dunno. Training alone is one thing, it's just that training against others makes everything so much faster. Like - I can't truly improve if I'm not training against someone, somehow. 

How does that even work."
The young, dark child started wondering what to do with his quirk and how to properly train it. The first step to truly improve would be to find someone who was close by and ask them for a small spar. Not even one where anyone could get hurt, he meant more of a Karate/Judo training where if someone got immobilized or pushed out it'd be A-OK. 
On a sidenote, it actually made him feel very very good about martial arts when eh found out that most of them were actually quite disciplined and great, where people didn't fight for aggression, but fight to learn self defense. Their spars were honorable and restrained, focusing on skill instead of violence.

Back to reality. Being the naturally sneaky, quick creature that he was, Kouta made his way to right behind Yuuto, his steps doing no noise mainly because he wasn't walking - instead, he flew all the way over to him. Once at a distance where they could talk, Kouta spoke up, completely unaware of how he might be startling the young guy who was training by himself as well.
"Hello! Would you care for a small martial arts sparring match?" 

wc: 404

Quick to the reaction as the boy always was, short moments after Yuuto noticed him and, quite quickly, reacted in an aggressive way by sending his summon to punch Kouta, the young boy raised his arms quite quickly in front of his head, blocking the punch so that it wouldn't go directly to his face and squish his nose, still not quick enough to the reaction to stop himself from being launched away, his body tumbling and rolling a bit on the ground. It hurt for sure, but it could be worse, actually.
"Owie! Sorryyyy! I'm Kouta, from Support Studies and I saw your Summon quirk and I wondered if I could fight it in a martial arts match, I'm sure it won't hurt you!"

Aside from being completely wrong and mislead when it came to summon quirks, Kouta, the "scared of fighting" boy seemed to be quite happy and open to the chance of fighting a Summon Quirk in a martial arts sparring match, ignoring his own pain or the danger he'd put himself in completely, choosing to instead step forward, perfectly white, beady eyes staring directly at Yuuto's, the young Itsuki somehow slightly taller than the summoner, making him actually look down for once.
When in a resting position, Shadow Monster Man was a bit of an unsettling quirk. Seemingly originating in his eyes, dark blue veins sometimes pulsated all over his body, almost too dark to even be noticed (unless under direct light), as well as somehow emitting an eternal "droning" sound, which also could only be heard in absolute silence.

That sort of presence that only got worse and worse the more alone they were in.
"You wouldn't mind that, uh.. would you? What's your name, anyway?" Kouta asked in his slightly cavernous, yet youthful voice, rubbing the back of his head to ruffle his jet black hair, attently waiting for his answer.

wc: 317

Why would someone as warm and kind as Kouta be flaring up those alarms in Yuuto? Maybe it was that overwhelming energy towards a fight that was simply so unusual for a boy like him -- which may or may not be influenced by his usual dosage of meds he takes daily to deal with both his quirk and depression. Couldn't be that, Yuuto had never met Kouta before, so he had no way to see this attitude as unusual. Maybe, though, he just didn't get along well with boys like him, of such happy, upbeat attitudes, even when desiring a fight.

Amped up on meds as he was, there was no way he'd even start thinking about the actual possibility that Yuuto's summon quirk would transfer its pain to the user, as the usual general rule of summon quirks. Like how Kouta's cape feels like skin, both for the good (like multi-petting a crowd of doggies), as well as for the bad, like when it gets damaged and it feels like his skin is being ripped and destroyed. 
Instead, all he thought about was how he just accepted the fight so, now, there were no setbacks!

"Alright! Let's have lots of fun!"
The first thing Kouta would do, obviously, is to test out the adversary's reaction time, as well as their speed of response. As he did it to so many others, this shark thing would be no different: by shuffling his feet in place at increasing, even inhuman speeds, his torso remaining as stable as possible, the shadow boy "disappeared", using a simple trick of the eye where, thanks to the sudden change in speed, there'd be a split moment where Yuuto wouldn't be keeping up.

Taught to him by Feng, it was called "Vanishing Step".

With this first "boost", Kouta moved at full speed towards the Summon, taking a little curve by the right to get to him, so that he could avoid Yuuto's eyes for a moment longer, looking to land a blitzing-fast kick to its side, not having the strength to match his speed (E Strength to D speed), since the young man was fighting with his body alone, forgoing the usual boost of his cape, figuring that he should continue to hone his body into a fine weapon, one that doesn't have to include his cape at all times, for it is not an entity without its weaknesses - like, under harsh light from a quirk, the cape is the first thing to go. 

wc: 412

That weird blend of Chinese Martial Arts taught to him by Feng and his quirk that's capable of super-human feats did indeed pose quite the confusing threat to those that weren't ready, including Yuuto.  Feng was actually even worse in how weirdly she fought, since her martial arts included a lot of more dance-like moves, to keep the adversary in a weird rythm, only to keep confusing them with sudden shifts whenever attacking. Kouta himself liked to be much more of a minimalist when he fought, doing only the necessary movements instead of being excessive. 

Excessive, though, was useful to confuse someone when they were better. So far, this summon was not better than him, at least seen in the first strike. Barely reacted, defended yet was pushed back and could not at all keep up with his speed, having gone invisible simply by going very fast. Didn't even need his ACTUAL invisibility skill.

"I'm not lazy and I wasn't put there by mistake! I'm training to be a spy and support studies teaches things that aren't combat and that I'll need! Not just silly violence!" 
Shuffling his feet around again, the now tell that Kouta was charging up his momentum to blast off again, he inspected Yuuto and his summon well. It failed his gaze when Yuuto reached for dirt so, to see him looking so confident and standing tall, it made him start thinking that he may have some strategy relating to predicting his movements. By this point, though, he was figuring that Yuuto wouldn't be able to keep up with his pace either and would grow tired before the shadow boy, so he had a new move he developed while training Vanishing Step.

It had no name.
Yet.
He started by vanishing from sight once again with sheer speed, only slowing down close to the summon's right side, apparently to strike him, his right arm raised to do so. 
It would not happen. Instead, he vanished again, his speed now flinging Kouta into Razor's back, winding up a kick. 
It would also not happen. He vanished yet again, now back at his front, winding up for one hell of an uppercut. 
It did not happen either and it continued to not happen for a good few seconds, where he popped on all four sides of the summon in no actual pattern to confuse Yuuto for as long as he could until the young boy predicted that Yuuto would figure out that, if he attacked all four sides at once, he could catch Kouta.
That one time, he'd actually only stop right above the summon instead, legs crouched down as much as he could before he shot them out, attempting to kick him so hard he'd bury that summon into the ground, the lack of using his special "cape strength" once again making his attack not optimal in its power.

It also turned out that repeatedly moving at high speeds and going to almost still lows REALLY wasted energy. 
Thank god he didn't try that against a real bad guy.

Kouta failed to account for Yuuto's fighting experience that allowed him to entirely predict the boy's moves, his hands moving right to his eyes to block the dirt he was throwing, not having his eyes peltered with that shit, though still leaving his torso wide open for that heavy blow from the shark thing, Kouta's defenses being completely shattered for that instant, his body flung quite a good meters away, looking like he really had gone down for a while.
Still, in mid-air, the young boy's body twitched, an explosion of darkness rising right out of his neck, a sort of flowing, flexible darkness surrounded his entire body.

Finally, he outright showed his flight ability, his body vanishing while still mid-air, shooting back directly at Yuuto and his summon quirk. There was an unnatural amount of pressure coming out of Kouta as he loomed over both of them, his right arm, pushed backward, looked like it was growing, bit by bit, to become one fit of a giant's, not of a small guy like him.

"Then fly, my pretty!"

Freezing in mid-air to have stability, as if literally standing on a floor that did not exist, the Shadow Monster Man shot forward his right fist, his entire body twitching as all of his muscles tightened at once to channel strength straight to the tip of his "enlargened" fist, putting as much power as his quirked-body and cape could apply in that instant, the wind seemingly twisting around the flat face of that fist, sounding akin to a low, shaky yet menacing rumbling.
A jab that was strong, fast and technically great enough to send the summon and, by extension, Yuuto a whole bunch of meters away, taken with the sheer impact and the slight extra of the gust of wind released from the sudden stop upon contact, likely in great pain - pain that Kouta was not predicting, since he still truly believed that his adversary wouldn't be hurt as long as he only hit that summon.

"FLYYY!"

Yuuto sure had some amazing skills with that summon of his, taken aback by its transforming abilities, now aware that it could do so when it became a shield to soften the blow he gave him, looking on as he didn't even fall when he went backward, instead choosing to run directly towards Kouta with that shield held up. Obvious by now what he'd try to do, which was an attack by morphing the summon once again - he just revealed that the shark can do that, so Kouta knows what to do to defend. And yet, he also wants to know just how hard it can hit. Could it really punch through his cape or would it be soundly stopped when it came into contact.

Choosing to test it out instead, Kouta lost his stance entirely in one go, releasing the tension in his body, straightening himself up and even relaxing his arms, just letting the cape's tendrils wrap around his entire body tighter than before, to close off any small spots or openings it might leave out in a rushed transformation, a ready and full "armor" suit that would meet Yuuto's..spear. His spear directly.
The impact was strong for sure, the sheer impact and running start clashing against Kouta's chest and, as far as he was aware, working quite well since the young boy was pushed back a bit, the spear seemingly digging into his flesh more and more.

Thing was, Kouta just got pushed because he's small and not exactly heavy.
That spear was not progressing any further and, to make matters worse, the Shadow Monster's left hand reached up slowly, placing his hand gently on his spear, quietly caressing it once or twice to properly feel its texture. The entire time it felt like Kouta's white, beady and endlessly empty eyes stared directly at Yuuto while the support student inspected his summon in the middle of a fight.
"..Rough, yet surprisingly to glide your hand through. Scales, easily.." 
With some force applied on his left hand, he'd slowly force the spear to be lowered to his own side, still paying very close attention to Yuuto's actions, still looking very much like he was staring into his soul and intimidating it from inside. 

The way it did not hurt him at all, the way he was treating it as a non threat and even lowering it down like a parent would lower the sharp stick a child keeps waving around.. none of it was right.
"You sure can get a running start. I am impressed." Kouta allowed the shark to go back to the shield form, or whatever other form it had, before his tendrils on his right arm extended a little bit, wrapping itself into a cylindrical shape at first, made out of flowing darkness, so that it could tighten and reshape itself into the baton of the young boy's imagination, moving it around slowly, getting familiarized with handling a weapon that was already forcefully attached to him before he walked towards his adversary.

Slowly, armed and still holding eye contact, the young Kouta now looked to test his mental fortitude. If he attacked brashly, a counter with the baton would be easy to do and deal a possible finishing blow. If he kept his wits about him and didn't let Kouta get to his head, then.. it'd likely be another free strike.