Tetsumin

This is a story about Miro Takizawa, who was born and raised on the peaceful island of Sasaraijima, an island surrounded by mountains and ocean. This introverted girl has lived her first year in high school peacefully, falling in love and trying to make friends. Her peaceful life takes a sharp turn for the worse as she discovers the secrets of the "Tetsu-min." Dark secrets await her as these horrific entities endanger the inhabitants of this once peaceful island.

(Source: MangaHelpers)