from a design standpoint, i think this is actually spot on for a manga/graphic novel cover!
It's bright, vibrant, and catches the viewer's eye. Plus it's not SO bold that it hits "overload" [I haaate when book covers do that.] In fact, the cover gives a lighthearted, comedic feel to the story, which seems to fit perfectly given the synopsis.
And the characters are adorable and I wish to pinch their cheeks. And I am so on board for this type of story, webcomic or real comic. The concept sounds hilarious. [and if it were really on a bookshelf I would so buy it, I kid you not.]