They could be in a situation where they have to work together on a project for the school. Karuizawa Kei is initially hesitant because she doesn't trust Ayanokoji. However, as they face difficulties during the project, Ayanokoji's calm and intelligent approach starts to win her over. Their relationship then blossoms from there. For example, they might have to deal with a tight deadline and scarce resources, which forces them to rely on each other's strengths. This shared experience can be the foundation for their growing relationship.
I don't know for sure. The ending of such a manga can be quite unpredictable and might not have been revealed yet. You could try discussing it with other fans to get their speculations.
I'm not really sure if they end up together. Different people might have different interpretations. Maybe you can dig deeper into the manga and form your own conclusion.
There could be a 'kei and hikari baby fanfiction' where the baby gets lost in a magical world. Kei and Hikari then have to go on an adventure to find their baby, meeting all sorts of interesting characters along the way. They face challenges that test their love for each other and their determination to get their baby back.