TodoDeku Engagement AU
This is a female Midoriya AU, because Endeavor probably wouldn't set up an arranged marriage between Todoroki and someone who can't reproduce.
Inko and Hisashi are neglectful, Midoriya's name is Izumi, and Midoriya has two dead little siblings named Akatani and Akane (twins, male and female). Akatani was stillborn and Akane barely survived birth, so she was very sickly for the two and half years she was alive. The family is extremely rich, and Hisashi does business with Endeavor. Midoriya has a fairly powerful telekinesis quirk. Midoriya and Todoroki were introduced to each other at a young age (they didn't know at the time that it was because they were supposed to get married some day), and fell in love. Midoriya never met Bakugou. Much like Endeavor and Rei's marriage, Inko and Hisashi's marriage was a quirk/arranged marriage (Inko's quirk is stronger in this AU), with the hopes of creating a child with powerful pyrokinesis. if Akatani and Akane had survived, they would have had two children with powerful pyrokinetic quirks. Inko and Hisashi cannot risk reproducing again, because both the child and Inko would most likely die. Midoriya attends Shiketsu, and Todoroki didn't stop using his fire for long because he knew Midoriya. At UA, Todoroki is pretty cold and unsociable, but much like with Bakugou, several people won't leave him alone. Namely Uraraka, Iida, and Momo, who dragged Tsu and Shinsou along for the ride. Half of the school is in love with Todoroki, and he's completely oblivious to it. Momo, Uraraka, Bakugou, Kaminari, Shinsou, and Iida to name a few. Sero, Kirishima, and Tsu are a bit jealous because they like Iida, Bakugou, and Uraraka respectively. The entire class is really oblivious, and the fact he had his engagement ring tattooed on his finger and he wears the real thing when he has the opportunity should be a massive clue to him being taken. It should also just be obvious that they make him uncomfortable by pushing physical contact and friendship and relationships on him.
Completely unrelated, but Midoriya would like to destroy the entirety of UA. It's definitely not because she's jealous and possessive and protective. Nope.
Where would you ever get that idea from?