Problem is, after Volume 8, it starts going downhill, like Kitoh had to quickly wrap everything up, yet an entire volume was wasted on that spaghetti syndrome kid. It's like the gangsters show up as a way to get Norio killed and Mamiko pregnant, and Naozumi, the guy who was set up in the first part to be some sort of Yagami Light-esque megalomaniacal villian, starves while plotting to take over the world. Starves. Yes, you read that right. He was thinking so hard he forgot to eat.
Narutaru Volumes 1-8: Fuckawesome. 10/10
Volumes 8-12: the fuck izzis shit? 4/10