The narrative indicates that the sister is preparing to start university and is consequently searching for an apartment and studying for entrance exams, as mentioned in Chapter 7.
Although the author does not explicitly state it, it can be inferred that the siblings are not twins, and the brother is at least a year younger. This inference is based on the observation that the brother is never depicted studying for university entrance exams and his reaction of anger upon learning about his sister's impending move in Chapter 7.
In the final page, the sister expresses her intention to invite her brother to her new apartment, suggesting they can engage in intimate relations without concern for parental oversight. The concluding panel, which depicts her smiling, implies that the siblings have begun to communicate honestly with each other.
In conclusion, the story ends on a positive note.
Risking my OpenAI account being banned for this was well worth it