Yi Yu, 20 years old, is a cashier in a convenience store in a small black street.Five years ago, after her parents disappeared, Yi Yu found some strange things happening around her.These strange things often happen on Mondays. At first, the mineral water bought in the shop was filled with litchi juice, and the cake shop that I liked suddenly stopped selling cakes and only sold braised bittern. Moreover, these strange things often disappear or recover after Mondays.One Monday morning, Yi Yu suddenly found a lovely girl at home. The girl claimed to be Yi Yu's black cat for a year.Yi Yu doesn't care too much about the strange things that she is used to. She thinks that everything will return to its original state as long as Monday passes. Until the first morning of the second week, Yi Yu wakes up - "Why are you still there?!" With the appearance of a girl as the boundary, the strange things that happen every Monday after that no longer disappear, but remain as facts.These strange things began to erode Yi Yu's daily life.The most deadly thing, Yi Yu finds that these strange things are becoming more and more absurd