The Japanese call them hikikomori - people who’ve become so socially withdrawn that they refuse to leave their homes for weeks and even months at a time. Sasami Tsukuyomi has been attempting to pass her first year of high school despite being a shut in. Fortunately, her older brother Kamiomi happens to be a teacher at the school she is supposed to attend. With the use of the “Brother Surveillance Tool” she can view the outside world via her computer. Theoretically it should be helping her adjust to interfacing with people again... Instead, it's giving her an up close and personal view of the very odd Yagami sisters who have various types of “interest” in Kamiomi.