Ushinawareta Rakuen

Nishijima Kousaku, an university student, attracted by a high payment, takes part in the scientific expedition on a southern island, organized by Hazama, a professor from his university. However, a storm breaks out and the ship suffers a shipwreck. Members of the expedition are washed ashore and start exploring the island in search of professor Hazama.
But soon enough they notice that something strange is happening around them...

[Edited from vndbreview]