Which Hana? Volume 1

Hana Kisugi is a somewhat apathetic 28-year-old office worker with no luck at work or with men. One day, she missed a step on a staircase and...
When she woke up, she was in the body of a 17-year-old high school student named Hana Yamada. At a loss, she ends up living the life of a high school girl at the boarding house Hana Yamada lived at, Ikuta House. She’s surrounded by the responsible adult Haruki, and the high school boy Haruchika. She's having trouble not falling for all the guys around her, but she can't fall in love in someone else's body, can she? While she's worried about that, someone tells her HE'S in love with HER!
Will this Hana be able to return to her former body?!