Foreword: I erroneously marked this game as eroge and now it's the time to check out what it's really about.
Title: Ushinawareta Rakuen
Developer: Silky's
Date: 1995-04-14
VNDB link:https://vndb.org/v9147
Synopsis: College student Kojima Kousaku is promised a high payment for assistance in scientific expedition on a southern island. However, a storm breaks out and the ship suffers a shipwreck. The crew gets separated and they start to search first for bed and food and then find a strange temple in the jungle.
Structure: Pretty much one route with minor branching.
Length: 4 hours
Game type: Mysterious island adventure.
Difficulty: Moderate. Several saves will lead you to some happy ending, although getting all happy endings will probably require a guide.

Character Design rating: 7/10
Protagonist rating: 4/10
Story rating: 7/10
Game quality: 7/10
Overall rating: 6/10
Rating comments: Game is thrilling and something constantly happening keeping you glued to the chair. So while playing it's totally fascinating, but the aftertaste is bitterish due to several shortcomings.
Protagonist: Usual college student, nothing really outstanding.

Characters: If we count only happy endings, they're only for the three girls. If count possible H-events, there are six characters. Characters seemed quite cliche to me - an active red-haired Ayano, a shy megane Yumi, professor young wife Shiori fills ojousama role, there's a blond american origin girl Monica and sexy mature professor secretary and partner Reiko, there's also the ingenious shaman girl Lira. They all share the same one-road story with minor branching leading to different girls happy ends - like go along the coast and that somehow means a happy end for Ayano, go by the forest and get the Shiori happy end. No meaning at all in that choice. Character design is great for all of them, but without voicing and with such small volume it's hard to start to feel sympathy.

Story: The story is depicted quite shallowly. First acquaintance is with the local flora that can cause various effects on eating and fauna presented by tentacle monster beasts, who rape some girl, but never harm anyone leaving peacefully afterwards. Then we discover the jungle village where professor holds supremacy. He throws the crew in prison and makes them to participate in a ritual ending being trapped in a cave with tentacle monsters. Professor boasts that three years ago he made the first contact with the villagers of this island and they agreed to assist him if he can keep the tentacle monsters away. Somehow he managed to lock most of tentacle monsters in a cave. But most important are special fruits that grow in this location and turn humans into beasts - professor is going to use them militarily later. The crew manages to find a way to the inner temple of the cave with some high technology ancient device inside as well as a mutated monster to oppose. And couple events later the end.
CG: The CG here are great but not too many for not a long game.

Sound: Music was actually great. Lots of memorable tracks. What was especially cool is some midi sound that resembles a cry a lot and it's used in all the situations when a girl is in danger and she screams loudly. At that time music stops and after that some dangerous music starts playing - really good sound support.
Overall comments: So game is thrilling, good-looking and memorable which is a lot. So here are the shortcomings the game is blamed for:

1. Heroines happy ends depend on quite a random looking choice and are difficult to get without guide. And those happy ends are a short talk and couple of HCG, not really satisfying.

2. The story is too short if all the 11 bad endings are cast away. So game has bad endings chasing in mind.

3. Repetitiveness of actions is big since heroines "routes" branch quite early.

To sum it up, game is short so it tries substitute volume with repetitiveness, fake happy endings, lots of bad endings and artificial rise in difficulty. Read it once to the end and get some happy ending and you're going to get a very good impression. But get all of three endings and your evaluation might fall as you get close to nothing for much additional effort.