Michi really wanted to be a princess but Ozai's expressions make it obvious why this relationship didn't last. Mainly because expecting a teenage boy to be married and mature is kind of setting yourself up for failure...

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Michi really wanted to be a princess but Ozai's expressions make it obvious why this relationship didn't last. Mainly because expecting a teenage boy to be married and mature is kind of setting yourself up for failure...
To be fair, Azulon had no clue where Ursa was and Michi was the youngest option they had so...they had to make a few compromises. And given the time period this isn't out of the question...Ozai was not exactly happy being a parent. Michi had to pressure him into giving it a chance...he did. It wasn't good but it was better than how he treated his other kids later on.
More Michzai headcanons
Yoyng Michi and Ozai tried to make the relationship work despite not really understanding what love really meant. They were 13 and 10 when the bells rang and Azulon was rushing to put Ozai with someone. Michi was just the youngest option so they waited until he was ten to get them together officially.
Michi was hoping for a more happily ever after with her prince charming like in the books, and whilst Ozai was a prince, he was not charming in the typical sense and was annoyed when she tried to make him live up to these expectations. Ozai is a warrior prince so expecting him to be lovey dovey didn't really work despite her attempts to mold him into it like a cookie cutter.
Michi and Ozai's interests were entirely different. Michi liked reading, gardening and baking. Ozai cared more for bending and fighting. The only interest they shared was politics but Ozai was clearly more ruthless despite both valuing the Fire nation's goals.
Michi was more physically affectionate but Ozai always kept chiding her on public affection. Any displays of affection are controlled, like Ozai holding her hand or hip. He doesn't like people seeing public displays of affection and finds it embarrassing so Michi kind of has to wait until they are away from public to where Ozai will begrudgingly let her touch him, albeit within limits.
Michi often gave Ozai flowers and baked a cake for their anniversary. Ozai didn't care much for the flowers but he did prefer the food. Still he kept the flowers in the family garden as to not clog up his room.
Michi did Ozai's hair whenever he was low on time. She is a good hair stylist though he made sure she didn't get too creative(she once gave him buns and he didn't like it).
Ozai isn't good at gifting Michi stuff, so he just takes her out to fire nation festivals instead as he doesn't like the idea of not giving his wife nothing(Ozai wants to at least look like a model husband and giving Michi nothing would negatively impact his reputation). Michi loved the festivals but wasn't good at the games so Ozai often won the prizes for her.
The main reason for divorce was because none of their kids made it. It strained rhe relationship ans they had done this for way too long so they decided to call it off despite not hating each other. They had tried countless times for kids but none of them lasted long.
When they had their own families, Ozai tried putting that chapter behind him and goes as far as to pretend his marriage with Michi didn't happen and shoves the evidence away. Michi on the other hand doesn't really get why Ozai acts so closed off around her since she seems them as good friends.
Michi gave Ozai gifts even after the divorce but Ozai was always more distant about it. He doesn't get why she still gives him birthday cakes but he doesn't reject it despite being colder.
She still calls him Zai-Zai even after he's Fire Lord. Ozai tells her to cut it out but doesn't harm her. Just brushes her off or rolls his eyes. Considering how Ozai usually reacts to blatant disrespect of his title, this is him being lenient. Outside of Ursa, she's the only person who can call him that and not get beat.
Ozai does still like her...but ultimately knows they aren't compatible and even though he did love Ursa, he values power over romance and won't let it get in the way of his ambitions. Still he liked her enough to let her and Ukano have a spot in conquered Ba Sing Se.
Michi actually thought she and Ozai were besties and lowkey didn't notice Ozai's hands slipping or didn't notice his eyes drifting downward.