Katsuki Bakugo wasn't an idiot, he was a quite smart person. However, he didn't understand one thing: What the hell is between the goddamn nerd and the Glasses?
He has seen Deku playfully chatting with the latter before the Quirk Apprehension Test and there the damn weakling, who was usually "Quirkless" loser suddenly could move super-fast. It revealed that the greenette had a Quirk which he didn't use around school. Green sparks and heightened speed, he was faster than Glasses and very accurate too. Not to mention to have some extra tricks in his sleeve.
Then there was the U.S.J. attack, where the nerd simply outmatched everyone present minus the exposed brained freak, who could keep up with him. Oh yeah, because that thing was made to kill the Symbol of Peace. Then Deku went plus ultra, zipping around like green blur, overwhelming the beast's senses by being faster than that and punching it with the strength could be mustered by freaking All Might! Glasses on the other side went to calling help.
Deku also made to win the Sport Festival, keeping the first place all the three event, at the first one he was the fastest obviously, reminding from that the nerd took down the Zero Pointer from the Entrance Exam, in the third he simply put out the Brainwasher out of bounds, then he freaking speed-blitzed the Half-n-Half bastard, made the latter use his Quirk too and still managed to win. Following that he literally ran circles around Engine Legs and in the finals, he beat the tar out of Bakugo. AKA himself. And he did Quirkless style! Just to annoy him.
After the Sport Festival almost everyone chose a Hero Name, Katsuki settled at Ground Zero and Deku chose this one: Emerald Speedster: Fujin.
At their internships, the nerd took out the three Nomu at Hosu and the Hero Killer Stain too! He even got credited for his victories. Oh, and he was noted to throw daggers with his eyes at Glasses.
What the hell could make Deku that mad at Engine Legs in the first place.
Now they were in their classroom as their homeroom teacher went to sleep in his sleeping bag. Timing was crucial.
"Hey Deku!" called Bakugo the nerd.
"Yes Bakugo? What is it?" answered Izuku Midoriya.
"What the fuck is with you and Glasses? You two are acting weird with each other." asked him the blond.
"Well, the truth is." started the greenette his reply, but Tenya Ida was faster this time.
"We're brothers." revealed the taller speedster.
"What?" now most of the class was shocked and surprised, their ranks included Bakugo too.
"I thought it was obvious, but I didn't reveal it because it would lose their charade." spoke up Yaoyorozu.
"Are you kidding with me?" asked her Mina Ashido.
"There is no mistake, their Quirks are similarly about speed, it seems the younger twin AKA Midoriya is born with a newer Quirk in the Ida family, this explains why Midoriya-kun had disappointed look at Ida-kun today which is originated from the Hero Killer incident. Also they occasionally call each other with their given name, and both look up at Ingenium, Ida Tensei. Plus Midoriya-kun easily teases his brother about the latter's habits when he wants without an issue." interjected Shoto Todoroki.
"Thank you Todoroki-kun, but you're both wrong and right." said Izuku, surprising the others and mainly the bi-color haired teen. "Yes, I have a newer Quirk. Yes, I look up at the Turbo Hero. However, I am not related to Tenya by blood. I am adopted by the Ida family." revealed the Ida's greenette.
"Izuku is almost all the time trains his Quirk, this allows him to be easily faster than me and also much better." added Tenya.