It's mainly about the relationship and development between Sasaki and Miyano. It might include their daily interactions, how their feelings for each other grow over time, and the story of their youth.
One popular story could be 'A Day in the Park'. It's about Sasaki and Miyano having a sweet day out, sharing ice creams and having deep conversations. There are also those that focus on their school days like 'School Festival Shenanigans' which details their experiences during the school festival, with all the cute interactions and misunderstandings.
The two central characters in the 'sasaki to miyano first years novel' are Sasaki and Miyano. Sasaki is likely to be a more confident character, while Miyano may be more reserved. Their different personalities play an important role in the story as they navigate their relationship.