Satsuki Inanae

Satsuki is Akira's childhood friend and his classmate. She believes that she is like an older sister to Akira. She calls Akira "Ah-chan", which he seems to dislike. She eventually awakens to her powers as the shiki tsukai of May in third volume of the manga. On volume 4, she has finally become a full flege Shiki Tsukai of May wielding the May 5 Red Coral shikifu. (Wikipedia)