Yui's post-marital life in " Protect Sweetheart " referred to Yui's post-marital life in " Protect Sweetheart." After Yui's marriage, Yui and Yameng were still good friends, but in Yui's family, Yui and Miki Miyuki became family.
Ayato would likely become more possessive. Since Yui is carrying his child, he would see her as even more precious and something that belongs solely to him. He might be more affectionate in his own rough way, like constantly checking on her and being more touch - sensitive.
Well, without having read the 'corrector yui secret revealed fanfic', it's hard to say for certain. But generally, in fanfics, when there's a 'secret revealed' part, it often involves some sort of plot twist. It might be that Yui has a secret identity or a hidden past that the corrector discovers. It could also be related to some special powers or relationships that Yui has been keeping under wraps and are now being exposed.
Well, perhaps in the fanfic, Ayato might see Yui getting close to another character, like a new vampire in their group. This makes him jealous as he has feelings for Yui. He starts acting more possessive, trying to keep Yui away from the new guy. Yui, on the other hand, might get jealous if she sees Ayato spending a lot of time with a female vampire who has a crush on him. She could start to doubt Ayato's feelings for her.
The main characters are obviously Ayato and Yui. Ayato is likely a complex character, perhaps a vampire with a strong personality. Yui is probably a human or a special being in the vampire world. Their relationship is central to the jealous fanfic, with their emotions of jealousy driving the plot.
One common theme is the development of their relationship. It could be about how they overcome obstacles to be together, like dealing with family issues in the Diabolik Lovers universe.
Another theme might be conflict. There could be internal conflict within the characters themselves, like shu's reserved nature conflicting with his growing feelings for yui. Or external conflict, such as other characters trying to come between them. Additionally, themes of self - discovery are also possible. As yui and shu interact, they might learn more about themselves and their place in the story's world.
One idea could be a story where Yui Kodai discovers a new quirk ability within herself during a tough battle. Maybe she's able to use her size - changing quirk in a completely unexpected way that turns the tide of the fight.