It's hard to say for sure. Both the anime and manga of Jitsu wa Watashi wa have their own fan bases, and popularity can vary depending on personal preferences.
I'm not sure exactly as I haven't read it. But generally, a light novel often involves a unique story, perhaps in this one it could be about a vampire (kyuuketsuki) and their daily life including an afternoon nap (ohirune).
The story of Kotarou wa Hitorigurashi manga centers around Kotarou's solo journey. It shows how he copes with daily life, makes friends, and faces difficulties, all while being on his own.
It could mean a lot of things. Maybe it's a name of a special being in the fanfic's version of the Naruto world. It might be an elf - like creature that has some kind of power that can't be tamed or understood, which is what 'yaserarenai' could imply.