Being that this is a doujinshi (read: fan-made manga), one cannot go in expecting anything typical of normal serialized manga. The artwork is AMAZING and outright beautiful, and the story is bittersweet indeed. However, I have no regrets in reading it. The ending may be a tad difficult to comprehend, but spend a moment on it, and you'll understand.
Here's my opinion on the story.
At the end, the number Shiroyama left was Tsukimura's number, not her own. This was because Shiroyama wanted him to follow through with his crush, for several reasons. One is because she liked the MC (main character) and wanted him to be happy, another is because she knew she wouldn't be able to get him. Plus, she already tried and he declined. In a sense, the MC is right in that it could have been any guy that found out and acted as he did, and she would have opened up to that person. This is likely another reason why the MC declined, because he felt her love was misplaced to begin with.
A lesser but still relevant reason is likely because he was too shy and too nervous to go out with her, especially given her rather aggressive personality "(Her) speech and manner was too stimulating for me at the time". Notice the "at the time". It meant that later on, he felt that he would have been able to handle her.
He also didn't have the willpower to go out of his way and attempt to help her. It was only until it was too late that he realized how serious in trouble she was. It was only at this moment where he probably realized that he held stronger feelings for her than he thought. However, it was too late by this point. The chance of contacting her was slim to none and she clearly meant for him to move on as well, hence Tsukimura's number.
The snow at the end is a metaphor for Shiroyama. It falls and melts; that is the extent of its life. However, because it falls so persistently, without slowing down, it can be said that the snow lives its life at full speed, or to the fullest, despite the shortness ("ephemeral") of it's life. Shiroyama is similar in that she was stuck in terrible circumstances, but just like the snow, she persisted, worked as hard as she could, and most of all, stayed as positive as she could have been throughout. She lived her life as best as she could despite the circumstances. She didn't die at the end, but that period of her life is akin to the snow.
That period of her life with the MC was also an inspiration for him. It inspired him to be strong like Shiroyama and the snow, even if he isn't admirable. And that strength led him to finally confess and presumably marry his crush, Tsukimura, at the end.
In conclusion, the moral of the story is to live life to the fullest, despite what circumstances you're in. It may suck and you may feel it is unfair and difficult, but the only thing you can do is to persist and live on as hard as you can, as that is the only thing that will make your life meaningful for yourself. It's true that the events of the story aren't perfectly positive, but the state of mind of the MC and Shiroyama at the end are. They've both moved on to living their life as best as they can. If this isn't a positive message, I'm not sure what is.
(-46)
