Humans are at war with robots and the machines are at the upper hand. Everything is destroyed and the defenseless humans are living in the rubbles, out of the robots' sights. A normal human girl Nanami has been living a poor but content life with her sister and her childhood friends.
However, everything changes on her birthday. The robots discovers the humans and Nanami only escapes a certain death because she is away from the shelter on that day. Upon hearing her sister's death, Nanami is inconsolable with grief. The only thought on her mind is “What if I have not wondered away from the shelter?”
The “what if” part happened, for she meets the friendly robot Kagome who grants her the power to travel back time and change history. With this power, will she be able to save her sister, fall in love with the man of her dreams and become the light of the world?
