I searched Comedy + Yaoi and this popped up on top, and I am so happy. This is my second favorite manga; it deserves that high rating.
Comedy? Well obviously, check.
Fluff? Double check.
Chizu? Chizu? Chizu is so precious, I s2fg.
The thing about this manga that I loved was that its balance was... just so right. It had a dose of drama, but at the same time, it generally kept to a lighthearted mood while neatly building character development.
Of course, I'll admit that sometimes, the plot seems somewhat contrived...
(Slight spoilers)
I agree that it was a bit frustrating that the characters all had to go through colds in order to open up to one another. I wish the author had been a little more creative on that front.
However, I don't think the colds were enough to detract from the manga. First, it's somewhat understandable that the characters get colds; one person came down with it, and spread it throughout the household. I've had that happen in my family before... it really was not a pleasant experience. The only difference was that we simultaneously got colds (in that it spread to my parents before I fully recovered), whereas in this manga, each person "rotated" it, lmao.
Secondly, I prefer the cold as a story vehicle over other alternatives, such as unnecessary jealousy or miscommunication. Of course, this story had a bit of both, but they weren't crucial (i.e. directly related) to the plot. And the thing is, this manga could have easily taken that route; for instance, the ex-boyfriend that came back could have been more persistent. And that would have ruined the manga...
So although this manga has a noticeable flaw, I'm still willing to overlook it and give it a 10.
With that, let me go reread it.