kasane Teto has the numbers "0401" and under those numbers it says her name in small print on her left arm. Meaning April 1st as 04 is the fourth month of April and 01 is the first day of April. You may know it as April fools day. april first is kasane teto's birthday because she was created as a joke vocaloid from crypton for April fools. she is not a vocaloid but is a utauloid which is much like vocaloid but it's free to use and easier to handle.