Sumika Sumire 

Is the inside of a high school girl actually 60 years old?! Sumire Kisaragi has been caring for her grandmother, father, and mother for a long time, and before she knew it, she was 60 years old and had never fallen in love. One day, after her mother's funeral and finding herself alone, a cat named Rei appears and says he will grant Sumire's wish to "relive her youth." Sumire is rejuvenated as a 17-year-old girl named Sumire and will be attending high school!?