A scientist, upon the death of his wife, began research into "Undying", so as to not lose anyone precious to him. His idea and logic goes into how strong emotions, such as desire for food, greed etc, is possible to rise about physical body. His experiments proceeded well, but much to his horror, he realized that he was not the one conducting the experiments...
It was his daughter, whom he did not believe would be as talented, and whom he assigned to take care of the guinea pigs. It took him a long time to realize that, and far too long. By the time he realized it, his daughter has taken over, and he tried to snatch his work back, only to let the guinea pigs go out of control, leading to his eventual death...
His daughter had similar ideas, except, as you may have guessed, would be strong emotions for hope, or what we would call, "dreams". Her experiments resulted in a successful result, and 3 possibly evolv-able products. However, she had to keep them in check. On her way back to the ship where the experiments were conducted, she met several people whom she asked to escort her back. A timid boy, that was touched and cursed by an incomplete Mushi-Host. A spy/assassin to steal the data of "Undying". One of the members of the rich organization that funded the "Undying" research. When they reached the ship, it was far too late.
The daughter ran to retrieve/burn her data(I am not sure what exactly she wanted back then). The spy wanted to retrieve the data for his country at first, but interacting with that rich member, and him asking for the spy to join him as a family, made him think otherwise. While he does not believe that he should really follow this rich member, he decided that such research would put the world in crisis, and possibly endanger what might or could have been his sister, the child of the rich member (Revealed to be Arisu in the end). The timid boy wanted to find a solution to the 'curse' he bears, the only way he could survive. The organization wanted the rich member to salvage whatever information he can from the ship, to continue the "Undying" research.
On the way back to the ship, they met a being in a theme park. A being that decided to claim this theme park as his own territory. A being that was once royalty, but was sent abroad to be rid of. He then was used as an experiment, and yearns for the right and powers he should have obtained, the perfect symbolization of greed. Later on, when he is separated into many smaller fragments, his desire for his castle, made him materialize churches that would hypnotize people.
The timid boy, cursed, met a woman, feeding herself with whatever she could find, even butterflies. A woman that symbolized the desire for food... The woman that eventually became "Gluttony".
The spy met with a strange creature, a pitiful being, just before the ship was attacked.
When the successful result("Alpha") awoke from his slumber, he fired beams at the ship. And the final twist of fate began...
The strange creature, disappears, and as it disappeared, it merged everyone's consciousness and thoughts on the ship together, for a reason yet to be revealed, or perhaps because it knew that such a move would prove important.
The spy, had wanted a home, a safe world for his sister-not-to-be, and his encounter with the strange being, caused him to become a Host, of the same kind of Daisuke, but way more powerful.
However, without training, his powers were too strong for him, and his body took damage for every move. Furthermore, due to the great power he possessed, the King-who-failed-to-be and Alpha feared him, and attacked.Even so, for a safe world, he fought against Alpha, and defeated him, though failing to kill Alpha. He smashed the embodiment of Greed into small pieces and vaporized this embodiment that took the shape of many wriggly worms. He then sought to destroy Gluttony, but due to the twist of fate, he failed...
The timid boy met Gluttony. The timid boy feared death. The timid boy wanted to find a way to live. The timid boy... became a Host, the Host of "Undying", the bug that cannot die. The bug that can keep Gluttony living forever, as she can use the powers of any bug she created in the world.
Gluttony escapes. And the weakened spy was assaulted by the true failed-king, as he could actually take possession of another's body. However, the spy may have seen this coming, as he had injected his body with poison, leaving the failed king with a rotting body, thus setting his form for future appearances.
And so that led to the beginning of the Mushi war.
Who's fault was it? The scientist or hisdaughter, who started the research? The organization and its members, who funded the research? The timid boy, cursed by an incomplete Mushi-Host, and sought to live, thus allowing Gluttony to live and escape in the end? The spy whom, should he had been more trained or well prepared, ended the entire battle there and then? It could well have been just a series of coincidences, or fate, but no matter, their wrongs cannot be undone, and thus, the Mushi war has begun, and will last for a long time to come...
