Dimensional Shenanigans
Izuku Midoriya, 3rd year UA student was walking down the street when he felt a feeling of vertigo overtake him, he stopped, closed his eyes, and waited for the feeling to pass. When it did he was standing in what looked like a gymnasium, there was a group of people standing in front of a whiteboard whilst what looked like a 15 or 16 year old was explaining what looked like a battle plan to the people. Izuku walked closer quietly, not wanting to be seen or heard, in case they were villains, when the 15 year old spotted him and stopped explaining.
"Good, another one, welcome welcome, my name is Owen, you've been sucked through the multiverse by my friends machine there"-Izuku looked over at a complicated machine he somehow hadn't noticed when he first arrived-"so that we can surprise a different friend." The boy had said that all in one breath, Izuku noted, perhaps someone similar in nature to Nejire.
"What" Izuku replied, using his intelligent brain to formulate the perfect response.
"Yes, we'll be using another one of my friends machines to travel back in time and prevent the fall of Rome, Jerusalem, Constantinople, the burning of the Library of Alexandria, take part in the Napoleonic wars, world war 1 and 2 and the clone wars, etc, etc, now hurry up and listen to the plan."
Izuku, in a marvellous stroke of genius, said the most intelligent thing to say in this situation that came to his mind.
"Huh?"
Pilot Jack Cooper was currently inside BT, fighting Slone to prevent the activation of the Ark when a feeling of Vertigo overtook him, which was weird, seeing as he wasn't doing any pilot like stunts so he brushed it off, but, before his eyes, the scenery, the universe melted around him and reformed into a different place, a gymnasium of some kind, just barely tall enough for BT.
Jack disembarked and surveyed his surroundings, BT was fine, though he looked shaken, he turned around and saw a small group of people, all going over dozens of different weapons Jack had never seen before, so, he did something very smart-
-he pulled his own weapon in them and began screaming "Where the fuck am I?", but he didn't get past the "Where" when the air was knocked out of him by a-is that a fucking 6 foot tall toad?
"Ah, you should be the final one, I'm Owen, I would point out the machine that brought you here but it has finally tore itself apart and scattered itself across the multiverse, you're here to help me surprise my friend, we'll be going places, but, right now you and BT are the only ones who don't know the full extent of our plans, so Kakashi here will explain it to you later, now give us all your weapons for examination, we want the best armoury for this, no?" A 15 year old is in charge of this operation what the fuck-
"Affirmative, you may examine my weaponry, Owen." BT is too trusting for his own good, how though? He is a military machine. Perhaps you know?
Issei couldn't believe it. He was getting the chance to fight in the legendary battles Azazel told him about. And! He gets to go back home when he's done! Transported back to the very second he left! It's awesome, and he also gets to do it with all his friends and loved ones! The whole peerage was here. It would be fantastic, a bonding experience and a unique way to get stronger to boot! Issei couldn't wait, besides, with all these super powerful people around, what could go wrong?
Issei, of course, had never been in a proper warzone before, fights-gargantuan ones-but never a warzone.
He might still have fun though.
Who knows.