Why IzuMina is my favourite rarepair (and one of, if not my favourite ship in MHA)
I wrote quite a bit about them and why I love the ship so much in my phone notes which I'll be directly copying from so apologies if the post doesn't look formatted and written to be a post on here because it wasn't.
Most of these reasons are cannon things that have actually happened but a bit of them are also headcannons I can strongly see happening based on the two of them.
Reasons IzuMina is goated:
They both have very similar origin stories where they both rush in without a single thought to help people in need despite the fact the odds are heavily stacked against them, Deku with Bakugo and the sludge villian and Mina with her 2 classmates and Gigantomachia. Also, they're both heroes for the same reason, they want to save people and form close friendships with their classmates.
They both have helped eachother, Mina was the one who taught Deku how to dance which meant he could fully utilize his body like Mina could in her dancing and more importantly her fighting, making Mina a very important part of his shoot-style and moveset - For Mina, like with many of his other classmates, he inspired her to be even greater by leading by example - In Chapter 430, it's revealed all his friends of Class 1-A came together to fund an expensive suit for Deku so he could continue being a hero alongside them, of course Mina being one of those people.
They both clearly care for one another, Deku & Mina have always been kind, polite and maybe have Mina's periodic playful tease in all their interactions, when Mina sees Deku mumbling like a nerd to himself she never showed any real annoyance, just a little awkward smile to show she found it funny how he acted - Not to mention when Deku was in the hospital one of the many times she was there to visit him and show true concern, this is shown further as she has a little heart to heart with him at the end of the vigilante arc, begging him to come back to her and Class 1-A, saying 'enough talk about being alone come back to us and let's have class together like normal!' She didn't need to shout out to him, she was exhausted and soaked from the rain and also being held by Kirishima and Iida, they had him with them but she shouted out anyway despite her exhaustion to beg him to come with them, Izuku expressed how he wanted to come back but felt like he couldn't to Mina and the rest of the class. When Mina has scolded Izuku it was only about hiding the true nature of his quirk, though that was moreso out of worry.
Opposites attract: Deku is an introverted and sometimes shy and timid boy especially in the earlier seasons, always being super nerdy and academic and analytical whereas Mina is an extroverted, loud, sociable and outgoing girl who struggles academically, creating potential for a great, healthy and beneficial dynamic between the 2. (More about that below)
Healthy support system for one another: Mina's outgoing, energetic and cheerful personality could act as a way to push Izuku to be his better self, counteracting his sometimes self-doubting and introspective personality - Izuku could do the same for Mina too, inspiring and encouraging Mina to be an even greater hero with his praise, admiration and guidance utilising his hero notes on her and his analytic skills!
They both have had times in their life where they got an upgraded version of their quirks and had to learn how to push past their limits to fight for what's right even though it meant seriously hurting themselves - Izuku has had many examples of this but one in particular was when he went far past his limits at the training forest to defeat Muscular and defend Kota and the rest of his classmates and pro heroes. Mina had her own version of this when she went beyond her known limit with her acid to protect Kirishima and Mt. Lady and the rest of the heroes present to defeat the sludge villian and melt through Gigantomachia's very tough skin with potent acid, causing her awakening where her acid changed colours and her horns got much longer. Since Izuku has much more experience with unlocking higher strength and pushing himself to harness it to the point of reaching higher limits without hurting his body he would definitely give Mina unique training to help her maintain her new power level without burning herself, probably using the same training techniques and imagining your power level as an image like the 'egg in the microwave' that All Might taught him right at the beginning.
The 2 have the potential for a healthy dynamic where they make one another even greater - Mina could show Deku his true worth since he had a very major inferiority complex early on and show him how to be more outgoing and sociable by leading by example, making him more confident in battles whereas Deku could help Mina with her studies in all the subjects she struggles in, showing her how to be more analytical in fights improving her overall prowess in fighting, combining her already powerful and flashy moves with deeper analytical thinking could make for an even greater hero! They could have, to Mina's dismay, study sessions where afterwards Mina crashes out from study fatigue with Deku being visibly proud of her.