Isshiki Tsubasa

Sister of the protagonist.
She works in an apparel shop in Tokyo and loves her job.
She is a mood-maker in the family because of her cheerful and lively personality.
She is very protective of the protagonist and is somewhat of a siscon.
She also thinks of Sayaka as a younger sister.
When she was a student, she had a dispute with her mother Ayame about her career path, but this has now been resolved and they are on good terms.