It's a jailbreak. Kijima sneaks out of prison during a storm and captains a boat to escape. The boat would be no good before the storm. Caught up in the storm, Kijima loses conciousness.

When he comes to, he finds he has washed up on some unknown island. He soon realizes to his annoyance that it is a deserted island, bringing absolutely no change from the sexless prison life he had before. However, 2 beautiful women end up coming to the island. It seems that they were tricked by some criminals and deserted on this island.
They were like deer released in front of a starving lion.

A suppressed evil instinct inside of Kijima is awakened.
"Now normally I don't thank nobody, but I gotta hand it to these guys. Thanks for going to all the trouble of bringin' me some easy prey."
In the setting of this crazy world, the story of Kijima begins.

[From DLsite English]