Dengeki!! Aegis5 (Volume)

is the first volume of the Dengeki!! Aegis5 light novel series, written by Nagaru Tanigawa and Illustrated by Nao Goto. It was released under the Dengeki Bunko Imprint in November 2004.

Synopsis
My parents ordered me to monitor my grandfather, who is known as a weirdo scientist, and I visited my grandfather's house. However, there is no grandfather, and for some reason he will live with the five beautiful girls who lived there, and this world is being invaded by something that is an invader of another dimension. The erotic artificial intelligence that manages my grandfather's house toward me who is struggling with such a situation laments, "For the past few days, if I do not look into the bath, I will not fall asleep." What should I do?

(source: Bookwalker JP - Translated)