I know, I'm late, but...
This is Author-kun's first series (I think? Last I saw was doing fanart) - so the art is quite inconsistent, but am giving him some time there.
There's a ref in the name that most Japanese would get that I haven't seen explained yet. It's a Japanese trope that rabbits (Usagi) will literally die of loneliness if you leave them alone too much. It's even kind of true - they won't die of it directly, but can cause them to become anxious, depressed, stop eating, and poof.
So basically she will die of loneliness unless he dotes on her constantly. This is very much a Noa-senpai situation!