Frightened Heart
The Frightened Hearts (Japanese: おびえるココロ) are objects in Densetsu no Starfy 4. They only appear in Degil's Castle (Stage 9-1). In the story, Okubyounomon asks Starfy to destroy them, as part of the 'Test of Courage' (Japanese: ゆうきのしれん). Removing all of the Frightened Hearts will banish Shinigami and remove the curse on Okubyounomon, turning it back to Yuukinomon.
There are 25 Frightened Hearts spread across four rooms. Each Frightened Heart can be destroyed with a Star Spin. Some of the Frightened Hearts are wearing a helmet, and take an additional Star Spin for Starfy to defeat.
As a reward for destroying the Frightened Hearts, Yuukinomon opens the door leading to Mayoinomon and rewards Starfy, Starly and Moe with the Degil's Dress Treasure.