On Chapter 173, the name "Raika Island" was found at the church room. On the next chapter Akira´s Death Tower Party found a picture with Raika Island on it.
The ecosystem found within the island comprises of extinct animals that interact within a relatively functional community. The abiotic factors that concern this ecosystem seems to have been derived from a modern environment - as indicated by all humans quick acclimatization to the environment. However, the animals comprising the ecosystem on the environment seem to orginate from significantly different era's, making any proper relations without natural equilibrium nearly impossible.
The biome diversity which defines the island is very unique and unnaturally abundant with wildlife.
The natural environment inhibits a system of underground caves, decidous forests originating from the Jurassic period, numerous mountains and shorelines.
There are extinct animals on the island from all over different time periods and different parts of the world. Mariya gives an explanation for each animal in the Encyclopedia of Extinct Animals and seems to be trying to figure out this major mystery of the island. There is a large majority of carnivores seen throughout the series all being on top of their own food chain. There are different animals in different locations with the only two animals known to have been in two areas are Canis Dirus and Arctodus Simus which had been seen attacking Yamaguchi's group in the forest and Rinzai Tooru in the mountains. However, this is most likely because the forest and mountains are adjacent to each other.
It is unknown how the animals are flourishing on the island despite being considered extinct. Everything about the animals remains a huge mystery.
After the Plane landed safely on the island, Akira Sengoku and the other passengers became stuck on the island. While they are waiting for help to arrive, they need to rely on their basic skills to survive on the island. It is necessary to do things you won't do it in your normal life. On the island there is no system that is right or wrong. There is only one true rule. The need to survive.
Throughout the island there are numerous groups of survivors. Because the chances of survival by yourself are limited, most people travel in groups. There have been a variety of groups throughout the series. All groups tend to have a leader who is leading the group and eventually may even join up with another group depending on the circumstances, willingy or not. There is an unknown amount of groups remaining, but a lot of groups have been seen throughout the story:
- All the characters throughout the manga (survivors scattered in below mentioned groups)
- Kouhei's Group (Dissolved)
- Makoto's Group (Merged with Akira's Group)
- Akira's Group
- Takashi's Group (Merged with Akira's Group)
- Mami's Group (Dissolved)
- Miina's Group (Dissolved)
- Kouichi's Group (Merged with Akira's Group)
- Unknown group (with Nagatsuka and Matsuki Noriaki)
- Nishikiori's Group (Merged with Akira's Group)
On this island it has different kind of terrain. From beaches to mountains. Akira's Group and other groups have travelled from the plane crash throughout the island. They even encounter some man-made buildings on the island.
During the stay on the island Akira's Group encounter many mysteries that has yet to solve. Even Shirou Mariya didn't have the answers for any of them (yet).
Since Mami Kagura can have premonition, so can we. Write down what you could expect from this serie.
- I think the plane crashed in the future. Many probably think it was the past, because of the extinct animals, but what if it wasn't? I mean, it's definitely not the present. If it was just because of the extinct species, then that could be the Jurassic Park scenario, but with the Tower having "Miina Isurugi - Rest In Peace" written on it, and the Miina we know is still alive, then... there are only three options - a) This is some REALLY weird memorial island/continent for some Isurugi who was named Miina, too (which is unlikely, since this Miina seems to be fond of extinct animals and the existence of those extinct animals on this memorial island would be dedicated to her) b) The Island is actually the supposed place of death, with the actual plan of killing her off. Or c) - This is a memorial-island for the very same Isurugi Miina who is on the Island, but several years into the future of the human race. I mean, think about it. It's definitely a memorial-island for a Miina Isurugi, what with the towers (crosses?), angel-statues, Isurugi Corp's symbol and the "Rest In Peace". We also know that it is as large as a continent, or shown as such, from when Akira's Group visited the Mountain. That on it's own eliminates the possibility of the Island existing in the present. Thus, I think the Island is actually a large continent (Eurasia? America?) turned into a wasteland. I assume it was once filled with humans, and that the extinct animals are experiments of Miina that were left to live around a specific area, until either the humans became extinct and the animals (with no one left to monitor them) broke out and dominated the whole continent. OR the animals broke out first and THEN the human race got wiped out by them.
- Then there's also the chance of some experiment going on, that somehow makes sense (although we don't know how, yet). Something similar to Blood Royale or the Hunger Games, but without them all knowing.
- And there's also the secret of Miina Isurugi (Real). Since she knows of all the weaknesses of the extinct animals, would it be safe to assume that she's been in that place before? Or that it was even planned out, all part of a project or visit there (wherever "there" is)? And what if she's only pretending to have amnesia and secretly knows exactly what's going on?
- As revealed in the last few chapters of Cage of Eden, the plane was said to have crashed on The Island in the future. In the present, however, Akira's mother becomes depressed, leaving work and even visiting her son's school everyday. Later on, she meets Miina Isurigi's grandfather and seeing that they both share the same grief for the "loss" of their kin, they begin a project that would be know as, "The Eden Project." That would explain everything on the island (The buildings, the animals, the technology, etc.) Since Miina was known to have an interest in extinct animals, her grandfather wanted one of the momunments dedicated to her.(hence one of the large towers with "Miina Isurugi, Rest in Peace" engraved on it). Later, it was predicted that due to some type of amoeba of a sort, the scientists on the island all die at once. And even later on revealed, Akira's mom is seen as an old woman, probably 50-60 years from the day she lost her son, who has adopted a girl to take over her place.
The passengers of the plane are spread out on the island. Throughout the storylines some have already died, some are still alive and kicking.
The timeline gives us how long Sengoku and his friends have stayed on the island. Some events are well documented, but others are hard to tell from one day to another..