From Chibi Manga:
Mayu is a high school girl who lost 2 years of her memories because of that accident. When she wakes up in the hospital, she sees her mother and her big brother, who says her father remarried 2 years ago. Her brother says that whatever happens, he will stay close to Mayu. Her mother smiles kindly. Mayu's memories end at the point a new family is made.... She wants to get back her lost memories. She wants to know, but it could be scary. This is what Mayu is told: "Mayu, you and I had a romantic relationship." What will Mayu do, newly bewildered by her brother's shocking confession...!? Big bro x little sis, a heart-wrenching, sensitive love story.