Histoire is a major supporting character in the Hyperdimension Neptunia franchise. She is the Oracle of Planeptune. She may look young, but she knows more about Gamindustri than even the oldest living human. Truth be told, she is actually the personified form of the tome on which she sits, born in Planeptune with the sole duty to keep a record of Gamindustri's history. Histoire's personality is very mature and serious. She does not play around and is very focused on her work as an Oracle, having to frequently nag Neptune to do her duties as CPU of Planeptune, and will go so far as to yell to ensure she gets her point across. While she is very hardworking, it sometimes takes her a while to provide people with the information they seek, usually taking her 3 hours, 3 days, etc.
Histoire appears in All Star Smashers as an assist character for Neptune, appearing throughout her moveset to explain both her and her older counterpart's movesets.