Birds such as cuckoos lay their eggs in the nests of other birds, and have their young raised by them. But it’s not only birds that engage in this sort of behavior. Humans can too...

Miwa Kanzaki has a busy life with a job in a main career track position at a major company. She has been married five years, and hasn’t had a child yet. Considering her age, she wants one soon. Her relationship with her husband, Hiroki Kanzaki, is good, but they both have busy work schedules, which are only getting busier. Eventually, Hiroki becomes indifferent to Misaki, and the rift caused by miscommunications between them widens. But despite this, Misaki still wants children. It is at this point that Misaki is reunited with Ryo Fuyutsuki, a friend who she often played with at the library back when she was in primary school. He always seemed appear out of nowhere when she was hurting, and would be there when she needed him. He was her hero, and the one she loved for the longest time. Now, he’s here to save her again... Misaki begins to harbor secret feelings for him. Fuyutsuki once harbored similar feelings, and it disturbs him to see she is not happy in her marriage. Eventually, the two cross the line, and she becomes pregnant with Fuyutsuki’s child. Misaki resolves to have the child raised by her husband. Her forbidden act of cuckoldry will change all of their fates. The story is propelled towards the truth as her daughter grows. What is this “love” which can drive people to madness? Where will this tale of love and hate that begins with cuckoldry go?