In the five years since Izuku Midoriya learned about his Saiyan heritage, he and Katsuki have made tremendous gains in their training. But unfortunately, his father hasn't been able to train him with the Ōzaru form due to the danger of the transformation as a little kid compared to a teenager.

In the meantime, the boys have been getting trained in martial arts. With as experienced an officer as Hisashi is, even with primarily being a scout and a scholar, Izuku and Katsuki learn a lot. Most of their training thus far has been in Saiyan combat styles, though the two have enrolled in a nearby martial arts school specializing in an eclectic style for hero hopefuls. Needless to say, the surprise of the instructors and other students when they reacted in sparring matches with completely unknown techniques brought smiles to the pair for days. They're at the top of their academy even without using extraterrestrial combat.

Then came the day for the next step in their training: chi. Hisashi ushered the two boys into his study to speak on the matter. The Saiyan man sighed and brought his hands up to his mouth, mulling his words over before looking at Katsuki.

"I know I've mentioned this before, Katsuki, but it's different now that the day has come. Do you remember when you were still little kids, and I told you and your parents about my heritage?"

Katsuki nodded, his face losing a little color from his nervousness. "Y-yeah, you also said I'd lag behind Izukkun in pure power, right? Does this have to do with that?"

"You're a very bright young man, Katsuki. Never forget that." Hisashi responded with a chuckle, ruffling the smug blonde's hair before returning to his serious demeanor. "Yes, you are correct. The reason isn't as simple, though. Chi is a potent energy, as you have probably learned on your own. It flows through the cosmos, permeating everything, living and non-living. Yet, despite this, and despite many humans being aware of chi's existence, no heroes ever use it. Do you have a guess as to why this is?"

Katsuki and Izuku looked downward in thought before the former came up with a response. "Maybe it's gotta do with quirks? Did quirks make it impossible to use chi?"

Izuku raised a brow and smiled at his friend. "That makes sense to me. Didn't you and Dr. Tsubasa say that my Saiyan genes and my human quirk genes were incompatible, and that's why I only have one and not both?"

Hisashi gave a thumbs-up and flashed a proud smile. "You both are spot on. While chi does still flow through people with quirks, those who possess any sort of quirk genetics at all are unable to use chi. Chi acts as a catalyst and a primary power source for all quirks, dormant and manifested. Because of this, chi cannot be used in a typical manner by a quirk holder. Technically speaking, whenever you use your quirk, you are using chi, but you are using it in the only way you can. Since Izuku possesses zero quirk genetics, he can use chi in a free form just like I can."

The boys nodded as Hisashi continued, immediately turning his attention to Katsuki. "When free, chi's typical expression is through physical enhancement. Focusing on one's chi allows one to use more power than their muscles can produce on their own. Even if you and Izuku have the same physical might, for example, you may be able to break a board with your full power while Izuku, after chi training, could break through a cinder block with his."

"Chi can also be manifested in a direct form through pure energy." Hisashi held out his hand and manifested a small ball of yellow light, awing the kids. "With this form of expression, one can create attacks like balls and beams or weapons like blades from their hands.

"This is what I will be teaching Izuku to do. I, unfortunately, cannot teach you to use chi because you already use it in the form of your quirk. So instead, I will train you to better control and use your quirk."

Izuku brings up a hand halfheartedly. "But Dad, is that legal? Don't you have to be certified as a quirk counselor and an educator to do that?"

Instead of replying with words, Hisashi reached into his pocket, pulled out two plastic cards, and held one in each hand for the boys to see. In his left hand was a quirk counselor's license, and in his right, a teaching license.

Izuku and Katsuki sat with widened eyes, and Hisashi chuckled, snapping the duo out of their stupor. "You forget, son, I may be from a warrior race, but I'm still very much a scholar at heart. My knowledge and your mother's connections as a government official made it easy to have my education verified and enroll in the necessary leftover classes. I was granted both licenses just after your second birthday, and I will renew them at the first opportunity once needed."

Katsuki jumped up from his seat with a fist held high. "Hell yeah, quirk training! I'm ready, Uncle Hisashi!"

As Izuku followed suit, shouting to the world his own excitement, Hisashi got up from his chair and wrapped both boys in a warm embrace. "I'm glad you're not taking this information the wrong way, Katsuki."

The boy in question lightly pressed his fist to his uncle's side. "I'm still strong as shit in my own way! It just means I need to work hard to do what Izukkun can't."

Katsuki glanced at Izuku, who practically had stars in his eyes. "Besides, I could never hate my brother for something he can't control."

"KACCHAN!" Izuku tackled the blonde bomb, hugging him tight as he let the famous Midoriya tears flow, much to Katsuki's chagrin."

Hisashi merely watched their antics with pride, happy that both boys were so close to calling each other brothers. Even with Katsuki's abrasive personality, no doubt inherited from his mother, he had no doubt the boys would go on to be amazing heroes.

/

"Hey, Deku, what are you writing there?"

Izuku sighed upon hearing Bushi Suzuki's taunt, firmly closing his analysis journal. He gave the finger-quirked boy an unamused glance while putting his things in his bags.

"Just more hero analysis, Bushi. You know I stay back to add new information, so give it a rest."

While Katsuki grunted and got up from his seat ahead of Izuku's, Iwaishi Saito came up from behind the latter and put his stony hand on the greenette's shoulder. "C'mon, Deku, we're just curious. Let us see!"

Iwaishi reached for Izuku's bag before being stopped by an explosive hand gripping his own. Both he and Bushi glared at Katsuki. The blonde boy held up his still-smoking palm, letting out small bursts while grimacing.

"Leave him alone, you snot-nosed bastards," Katsuki growled. "You know better than to fuck with anyone, let alone the two of us."

The pair of bullies just laughed at his threat, their frowns shifting into smug, eerily-wide toothy grins. "What are you gonna do, Katsuki?" Iwaishi taunted. "You know you can't hurt us without ruining your chances at being a hero!"

"Yeah, exactly!" Bushi added. "Why do you even bother hanging out with this weak loser, anyway? He just has a tail; us three are so much better."

"The fuck did you say about Izukkun, you asshat? You wanna fucking go?" Katsuki shouted. The threatening pops spread to both hands, burning hotter and brighter than before as he took a defensive stance.

"That's ENOUGH!" Came a shout from behind the would-be assailants. Katsuki's eyes widened at Izuku's uncharacteristic outburst. Bushi and Iwaishi immediately started to pale upon seeing the boy's snarl. The almost animalistic glare in his eyes had all three quirk holders frozen in their tracks.

While Izuku struggled to regain control of his breathing, he failed to notice the subtle shift in the air. Instead, his hair and the loose hem of his shirt began flowing along the new wind current in the room.

"I'm fine with you bugging me, I don't care, and you know I can hold my own if you think you're dumb enough to pick a fight with me, but I won't let you target Kacchan or anyone else. If you even think about hurting him, I will make you PAY!"

The more Izuku raised his voice during his rant, the more electrified the room around them all grew. Finally, the ever-increasing power reached a precipice as he screamed out his threat. The air in the room exploded outwards from the half-Saiyan child, shaking the entire building and cracking all the windows in the room. Despite their attempts to stay standing, the three observers in the room were pushed away and fell backward from the pressure wave.

Izuku slowly regained his composure, white-knuckled fists relaxing as his demeanor shifted to one of confusion and fear. What the…? I knew I'd grown stronger since I started training my chi, but I didn't think I had grown THIS strong.

Katsuki smirked, though without any bite to it, as he got up. "Remember, losers, Izukkun has a dual-type quirk. Ikari doesn't just give him the tail, but enhanced energy output."

Both of the bullies shakily nodded and bolted out of the room before they could be attacked or caught. Katsuki went over to Izuku, giving him a once-over before giving him a singular pat on the shoulder to gain his attention. The greenette looked into his blonde brother's eyes, holding a silent conversation with him. The pair nodded with determined gazes. They would talk to Hisashi again and work to gain control of this power and use it for good… after the detention they'll probably receive for the "quirk accident."