No matter how the story ends or how short it is, if the mangaka succeeds at leaving a deep impression on the reader, then her work can be called successful by all means. I believe that she did just that, bringing a lot of emotions in a limited space of white paper and black ink. Though this manga has both a tragic and "fleeting love" themes but it remains an impactful story which I don't regret reading.
Edited: I read this story again today (March 12, 2017). It had the same impact on me compared to the first time I've read it. I couldn't keep my tears from falling. I wonder if I will able to re-read it sometime in the far future without becoming all-emotional about it. Lesson learned from this: jump on the occasion the first time you encounter it, leave no regrets behind.
Tada, Kimi Wo Aishiteru