This artist drawing style is a little hard to follow, so I'll try to give a short summary of what I understood from images.
There's a yukkuri six-pack discarded into the trash (like food-grade yukkuri you would buy for your pet Remilia). Most of it's inhabitants either used or died in process of discarding, one koyukkuri Reimyu still survives and is "born" into the trash. There she is discovered by a couple of stray Marisas "hunting" that trash. They promptly proceed to damage her accessory and designate her as poo-poo slave. Later those Marisas fall victim to poisoned cake trap for strays, while shit-eater Reimyu survives and is freed. Timeskip, she grows up into Reimu and finds a Marisa that has lost her hat and uses plastic bag for substitute. Damaged ribbon and bag hat is a match made in heavens, so they proceed to breed like cockroaches. Soon after Marisa falls asleep, our Reimu awakens into fine Deibu and squashes all little Marichas - all but one that was sleeping inside daddy's bag hat. Later when now Deibu is either distracted or asleep, Marisa calls out one Reimyu, and proceeds to squash her into fine pulp. Squashed Reimyu's ribbon goes onto survivor Maricha's head and now she can get out of hiding in the plastic bag. Maricha's hat is remaining on daddy's head under the bag, giving daddy a bit of comfort. Koyukkuris (including disguised Maricha) proceed to happily eat squashed Reimu and wander away. Again timeskip I guess, it's now winter and they have food, but thermal isolation is inadequate. They are doing yukkuri pile, but it's not helping much. Some koyukkuris climb onto parent's heads. Then they proceed to pee in the sleep, with pee freezing into ice and stucking everyone together and to same place. Next panel is either a dream or a flashback, I guess. And final panel is happy end, thanks to mister cold.
Overall a nice story, but I would have preferred to see some more development into disguised Maricha story, in the end she did not matter at all.
Updated
The feeling of awaking already became an intense pain and was attacking Reimu.
Feeling the cold as if it was reaching to the core paste,
although on every daytime, she recovered that she was almost able to move her leg, eventually her whole body was frozen again at night.
The dream was very real and suffering.
Reimu thought she did not want to experience this dream anymore, and wished to awake and come back to the real filled with easiness.
She had a grudge against herself every time she met this dream.It was the 32th night from when the overwinter started, that Reimu was released from this dream.She could not speak even a word because the frostbite also froze her mouth inside. The ice cutting her mouth was painful.
She thought that at least only the good thing was it was just a dream, but the pain running whole her body did not let her to keep her thoughts clearly.In that dream, mister winter was not over.
Being released from long, long cold of the night,
receiving the benefit of the sunlight with the dawn,
melting her frozen body a little bit,
and Reimu awaked in the pain.
How many mornings came from when she was not able to move due to the frostbite?