Oni-Deka!

Kiryuin Hanao is the idol of her school and her childhood friend Takezou Watanabe is always by her side, helping her throughout her activities. But when she suddenly becomes a giantess, she is forced to return to her old ways in order to protect the city and her friends. However, it soon becomes apparent that Kiryuin is not the only girl to be afflicted with a sudden change in stature...