Shiranui Yoshikazu was born into a normal (relatively so) family, but his early life was one spent rarely out of bed.  He was born with a terminal heart condition that could kill him at any time, and he had a fairly lonely childhood, save for an older sister who was very much into tough love.  His life changed when a heart donor was found, and after the surgery he found that the girl who donated his heart now inhabited his consciousness.  Realizing that it would be difficult for them to coexist, he gladly gave up a part of his emotional spectrum, his ability to feel sorrow, to allow the girl to survive inside of him.  He named the girl Kokoro.

Shiranui had no dreams of his own, so when Kokoro spoke of her dreams of joining the Mars colonization project, he immediately chose to fulfill them for her, taking her along (literally) inside him to see the sights she so desired to see in life.  His iron will, born of enduring great pain and his self-inflicted sense of duty, pushed him to survive the horrifically harsh training conditions (think worse than boot camp) as well as the educational requirements.  He was so focused that he caught the interest of one of his fellows, one Ichijou Shizuku, who was seen as a genius amongst the younger generation of Japanese candidates.

He and Shizuku became comrades-in-arms, struggling to fulfill the requirements asked of them, that even trained astronauts had difficulty meeting.  When they won through, it wasn't so much a miracle as a matter of course that they left many of their fellows in the dust.

The journey to Mars was one-way from the beginning, and it was a given that they would spend the entirety of their remaining lives building the foundation for future colonists bit by bit.  Shiranui made friends amongst both the adults and his age group.  Kou, from the Chinese group, a sharp-edged but often cheerful boy who was more naturally capable than him.  Tyron, the black engineering head from America, a robotics expert with a childish sense of humor and a true frontier spirit.  Dimitri, the former Russian soldier turned mediator and leader.  His daughter, Tsunami, a genius biologist who finished college at the age of ten.  Maaya, the Swedish head medical officer with the gentle manner.  Last of all, Shannon Wordsworth, the brilliant and idealistic leader of the American contingent.

This small group became the central element of the expedition, which renamed itself the Calamity Monkeys, in hope that they would not make the mistakes found in so many science-fiction and dystopian literature.  For a time, they found joy in the process of slowly developing Mars.

The disaster began quietly, with the discovery of an unusual gem-like mineral clump found under Mount Olympus.  At first, it seemed to be merely an interesting research subject, but when one of the team members pierced their skin with one and fused with their body, the beginning of the end had come.

This gem, called Marscyte by the research team, gave the person it fused with immense physical and mental capabilities, as well as an ability unique to the person.  The various teams, up until then mostly united as colonists rather than divided by their former national allegiances, quickly broke back up into factions, other than the main group led by Shannon.  

However, this didn't last for long, as members were drawn back into their old groups one by one... and suddenly everything went horrifically wrong.  Four of Shiranui's friends suddenly began using immensely powerful abilities to slaughter the groups indiscriminately, calling themselves Disasters.  Dimitri became Volcano, unleashing and controlling magma.  Tyron became Earthquake, causing the earth to break apart and swallow those around him.  Maaya became Avalanche, calling immense waves of snow to appear from thin air and dropping temperatures around her.  Last of all, Shannon became Tempest, wielding the weather like a weapon to butcher even those who were using Marscyte.

At first, Kou was not part of this, but after a conversation with the former Shannon, who revealed that his sister's heart (sold by his parents) had gone to Shiranui, lost himself to hate and became Phantom Killer, wielding an invisible blade that could cut anything.

Shizuku and Shiranui fought them, one by one, struggling against their former friends, Shizuku sealing them away one by one before they were the only ones left of the expedition, slipping into cold sleep capsules even as their Marscyte shattered from overuse.  

It is difficult to imagine how horrifying their battles were, even with Higashide's excellent writing.  Loss doesn't even begin to cover it, betrayal merely skirts the edges.  Through all of this, Yoshikazu felt anger, despair, and many other emotions... but never sorrow or grief.  The loss of those emotions was felt as a wound, a gaping void inside him as he fought, even as he knew he'd lost his friends beyond all retrieval.