Romance is the way to made story, no matter what shape of the character. Here the romance is not the love of lover, but something between more than friend and less than lover, because each of them just had both of them to depend on.
As the story is about a couple of girl, that sadly one of them becoming zombie because certain disease. While the story progress the MC trying her best to fulfill the promise, while many hurdles coming to their way, yet after all, everything could be resolved in a good way.

For manga, even though it is quite short, it had impact that the plot needed to be, from the how they becoming friend to how she is finally passed away.
Quite enjoyable story.