Saena's apartment is Saena Mogami's apartment most likely located somewhere in Kyoto. It is the location where her first ever love interest, Kazushi Misonoi, visits her. Misonoi mentioned that he comes to visit her so she could help him study.
Her apartment is actually quite small and it is fit only for a woman like her, living alone without any family. When Misonoi visited her, there could be a small table seen in the living room. She also has her own computer somewhere where she does her work and a small balcony outside where she could get a glimpse outside her apartment.