北川 亜季

Keito's younger sister. She is a member of the badminton club.
In the olden days, she was very clingy to her brother and loved him a lot.
However, when Keito was living in the dormitory, he didnt contact Aki for 2 years since then she has been estranged from Keito and shows him the cold shoulder. 
But in reality, she can't help but want to be spoiled by her beloved Nii-nii.
She is very tsundere in nature.