Kioku Capsule: Oniichan to, Mou Ichido

Mayu is a high school girl who lost two years of her memories because of an accident. When she wakes up in the hospital, she sees her mother and her big brother, who said 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...!? A heart-wrenching, sensitive love story between a older brother and younger sister.

(Source: Futabasha, translated)