The Island of Hoozuki, Hoozuki no Shima
Hohzuki Island
Sanbe, Kei (Story & Art)
Right(→) to Left(←)
Manga Description

It’s about two children being sent to live on a basically deserted island. Deserted except for a few other kids and teachers. Suzuhara Kokoro and his blind little sister Yume find that all is not as it seems as they learn more from the other kids and see the actions of their teachers.