It's the Kaimei School Festival, and Bossun's class is doing a maid cafe. Everybody's parents show up, and Bossun is approached by a man who claims to be the doctor who delivered him. He has finally decided to tell Bossun the truth of what happened that day, which he has kept secret for 17 years...
It's impossible for two type O parents 
to have a child with type AB.
Es imposible que padres con tipo 
de sangre O tengan un hijo de sangre AB.
Es imposible que dos padres de
grupo O tengan un hijo del grupo AB.
É impossível que dois pais tipo
 O tenham um filho tipo AB.