Hiyoko's cute appearance, voice, and (initially) her way of talking give off the impression she is innocent and childlike. However, in her introduction alone, it is quickly revealed that she is very direct and cruel with a malicious side in how she squishes ants.
Hiyoko has been through a lot in her childhood due to her status as an heiress, explaining some of her mean personality.
her personality became slightly better during her school life, by https://www.deviantart.com/depraveddefense