This is the first work I read by Tsukumizu. And similar to Shemiji simulation I have rarely been so quickly convinced by the greatness of a manga once I put it down. This is a bleak and desolate story of two stragglers at the end of the world. There is a sense of quietness to the setting that resembles Blame! in more ways than one. This journey similarly takes the structure of that manga, following our heroines across vignettes of a world they never had a chance to experience. The two girls become spectator spirits drifting across a monument to the futility of humanity. Their interactions with different objects, characters and concepts feel almost like moral parables about different aspects of the human condition. While an accurate description, this is also a mischaracterisation of the manga. There is a sense of wonder and love between the two girls. The visual metaphor is apparent, a snowy firepunch-esque landscape and two wonderers in cosy clothing uplifting each other's spirits with the worth of their companionship. Before I ever read this I assumed this is a contemporary war story, and the atmosphere of one is there, even if no war seems to have been fought for god knows how many years when we first enter this world. The two girls have been abandoned and have no choice but to accustomed themselves to the horrors of daily life in this frozen over hell. This is both a heart-warming and devastating story of what it is like to slowly lose everything.
I can gush about the worldbuilding for hours, although I must stop myself to avoid spoilers. The key point is that while there is a strong tangible texture to the interwoven fabrics of society that used to stand there, the setting is also perfectly woven with the specific story of Chito and Yuuri. The nature of what happened, the demons lurking below our imagination, is obscured at the start similar to the inner lives of the two girls bubbling in this time of crisis. This is a story of two people who hurt each other with their unchangeable nature, who also would fight to meet the other in any universe. Considering the hair colour I'll pretend this is another example of the Ryu and Akira across media. Everyone they interact with reflects this isolation at the core of the story. It feels preposterous to question the timeless bond between the two girls until we see people lost in the search for food and meaning to their existence. Caring for another feels like enough to fuel one's life.
This is not close to the amount of themes the series covers and moods it embodies, but you should find that out yourself.