surimuki
Surimuki (lit. Scraped Girl) is an obscure character only known through finding a book in the Library.
Enter the library, go left to the last book in the first bookcase. You will be greeted by lined paper. Press enter and words will appear, she will pop up and giggle/sob. This note she has written says "すりむいちゃった。" meaning, "I got scraped."