Umi Sasamoto was in a traffic accident in her second year of high school and fell into a coma. When she wakes up 16 years later, she has a strange sister who is the same age as she was before she went to sleep. Umi is welcomed into her strange home with no recollection of her past. Feeling a strong sense of incongruity at having the truth of the incident covered up, she tries to trace her fragmentary memories (from mangaupdates)