Hidoi (ひどい Hidoi) are the main monsters in Season Heart Pretty Cure!. They are created when a commander of the Dusk Area shoots a Shard of Darkness into a human's neck. The commander then shouts, "Come forth, Hidoi, and release the evil in your heart!" and the human is then turned into a Hidoi. When they are defeated, they say "so relaxing".
List of Hidoi
|Episode #||Possessing||Summoned By||Defeated With||Origin|
|SHPC01||Scientist||Stone||Spring Flower Attack||Yukimura Ami, who wanted to become a scientist.|
|SHPC02||Skateboard||Stone||Summer Sun Explosion||A girl who wanted to be as cool as Chinen Akemi.|
|SHPC03||Baseball Bat||Poison||Autumn Wind Shower||A boy who wanted to become a famous athlete.|
|SHPC04||Camera||Stone||Winter Snow Blizzard||Yukimura Yuriko, who wanted to become a reporter.|
- Hidoi means "terrible" in Japanese.
- Like the Jikochuu, Saiark and Zetsuborg, they are created without fusing objects.