Even if this might be my first review on MAL, I still intend on diving straight into the heart of the matter (so forgive me in advance for my selfishness):
Although this manga's concept touches my heart in more ways than one, I was at first uncertain about whether I should read it. I almost did not bother: I assumed it would not end well because the manga was rather short. In the end, rather than sleeping, I decided to read it. Despite everything, it left me with an lasting impression. (I am going to have a sweet dream tonight, that I am sure.)
The major reason
for which I enjoyed this manga is probably that, like the protagonist, I have a tendency to escape from reality. Minor reasons include the manga exploring some aspects of existentialism, and unrequited love. Such features allow me to empathise with the protagonist and the 'heroine'.
So, if you have some time to spare, or if you also tend to run away from real life, it would not hurt to read this manga. It should not incite strong emotions, especially with limited character development: like this first review of mine, it practically goes straight to the middle of nowhere, and leaves you in the middle of nowhere, too. However, I would not go so far as call it lighthearted either. You might get some inspiration out of it, even.