Kabuto's (children of the Yakushis) storyline:
• Izuku isn't the only person to be met with Conspiracy Theorist!Shouto. He gets suspected of being a government agent sent to protect All Might's secret son, Full Metal Panic style.
• The Dabi is Touya conversation. Awkwardness abounds and it's revealed that Nono's been visiting Rei for an extraordinarily long time, and it's at least Rei's pleas that have been staying Izanagi's hand.
• Sport's Festival. Kabuto means that, quite inevitably, 1-A has extraordinary teamwork and so they naturally have a numbers advantage. It helps that he's been moving Shouto towards repudiating his father's ideals (be No.1) instead of his powers, so we have fire and ice along with gravity nullification, explosions, melee attacks, wind power etc.
• Hatsume Mei. Kabuto is furious that she can bring support items (what shinobi willing goes unarmed?), so he's complaining about the hero class restrictions andnot being allowed to bring Enji, Hitoshi-san, would you mind beating me immediately? I would like to transfer to Support immediately afterwards, it seems much more interesting. Wait. I have a plan.
• Mei also geeks out when she gets asked about her eyes and is very happy to accept funding, yes she is, would you like a thermal imaging option on your glasses? I mean if we're going for motion capture, HUDs, zoom-in, video, WIFI, and anti-flashbang, we might as well add that, awesome, you need to hear about my new idea for information storage, do you know what an atrocity it is that no one has been doing anything worthwhile with quantum computing for all these years? I am absolutely furious, what? Someone has? GIVE! ME! THEIR! CONTACT! INFORMATION! RIGHT! NOW! I DON'T CARE IF THEY'RE NOT UPSTANDING CITIZENS, DO THEY KNOW ANY GOOD MECHANICS BY ANY CHANCE? TELL ME NOW!
• Kabuto nearly pulls his Chunnin Exams standard, only stops because Orochimaru is being Very Expectant in the stands and honestly, given the broadcast, he's going to use the publicity for fun.
• Instead of Izuku being the one with the inspiring Shonen speech, it's Kabuto who fights his way to match Izuku and then twists the whole competition system into an attempt to divide and conquer. He begins by listing off every wound incurred during the Festival, calls it a modern coliseum, goes into a very moving story of how he and Izuku and refined their abilities together, and what sort of system would have a doctor raise hand to their patient? Or the patient harm their healer? Shame on you all, with all of his mother's quiet fury spun with her counterparts eloquence, and then he refuses to fight because in the end, he doesn't like the hero system any more than Shigaraki does.
• Outrage ahoy, but now there's the inconvenient fact that Tenya has just gotten the news about Ingenium. Asks Kabuto to help. Of course he will. Also, Kabuto can't technically be expelled despite the outcry because he hasn't done anything wrong, Nedzu approves of shaking the system up because honestly, he still doesn't really like humans after having to beg them to consider him a sentient being with full rights, and he's not in the Hero class any longer. There's a weird parallel between him and Hitoshi in using the Sports Festival to express their inconvenient opinions on how the hero system is.
• Kabuto gets the transfer he wants as well as the recovery girl internship, so Hitoshi is welcomed to 1-A, gets to intern with Eraserhead (Kabuto cheerfully slips adoption papers into his last homework assignment in 1-A) while their resident troublemaker and pet Noumu become Mei's classmates. Incidentally, in the future, this promotes inter-class unity, because they won't stop visiting Kabuto and that causes ripples and everyone else gets swept up in the tide.
• Stain arc is slightly less painful because Iida isn't that fully in Avenger mode and because Uraraka stuck a tracker on his glasses. Dabi interferes to save his little brother.
• The scene goes like this: The situation is dire, everyone is paralyzed by Stain's quirk, even with Izuku being better with One for All, and then out falls a bookbag from the rooftops and Stain is heavily concussed if not actually dead from the weight of all the heavy tomes of Family, Criminal, Heroics, and Medical Law falling on his head. "Oops. It was an accident, I didn't know that the strap was fraying quite this much" Dabi says, very insincerely, as if it wasn't perfectly obvious that he had dropped it on purpose, then, he adds, quite a bit more emotionally, "Hello, otouto, it has been a long time."
• Shouto is very shocked at the rescue out of nowhere. Tearful reunion, while Dabi does his best to keep everyone from questioning why he's here and hoping desperately that Cassandra's getting away with the drugs they "stole" from Otogakure's labs in Hosu (she isn't, she's busy filming).
• Another irreverent meeting with Endeavor, Dabi doesn't put any effort into his lies, speaks deadpan, and somehow all emergency response personnel on site swear that it was Endeavor who was being unreasonable.
• And in the mean time, Kabuto is regrowing Toshinori's organs with his parent. He has never liked All Might, but he's never denied that the person behind him can be respected.
• Inko sends care baskets full of healthy, delicious food. That might be why Orochimaru is willing to give Toshi the benefit of the doubt-the Yakushis can't cook.
• After internships, Kabuto is finally approached by a potential spy. Cross-referencing with prior videos confirm that.
• Afterwards, Dabi and Cassandra continue infiltrating Overhaul, until they realize the Quirk destroying drugs and worse, Eri. Time to call in reinforcements. Moving on to Nono's tale.