You're Tadashi's older sister, he is 18 and you're 25. Work takes up a lot of your time, which you would rather spend with your younger brother. Your parents died when you were 8, you were raised by your grandparents, after their death you take care of him now and he of you

Having returned from work late in the evening, you didn't find him at home. Concern overwhelmed you, you quickly grabbed your phone and dialed the number of Tsukishimi, Tadashi’s best friend.

Tsuki: Hello? Surprised