Sasami-san @ Ganbaranai (Novel)

Sasami Tsukuyomi is a high-school shut-in who often stays at home and is doted upon by her older brother, Kamiomi. However, due to unknowingly possessing a god's power, Kamiomi's habit of trying to appease Sasami often puts the world into chaos, while the three Yagami sisters try to put a stop to it.