The things is that, differently from Igarashi, who never saw Natsumi as anything other than a friend, she sees Yuto as someone special. She fells at ease with him, she likes to watch them from a distance, she lets him go into her home(her special place), and much more. Natsumi drama is about the fact that she went from merely finding his tries amusing, to actually developing a emotional bond with him. She may not want or have what it takes to answer his feelings, but she doesn't want him to go away