Youkame no Semi

Kiwako Nonomiya is devastated after Takehiro Akiyama, the married man she has been having an affair with, manipulates her into getting an abortion by promising to marry her and then refusing to divorce his wife. Kiwako then learns of Takehiro's wife's pregnancy.
One morning, while Takehiro and his wife Etsuko (Yuka Itaya) are away, Kiwako sneaks into their home to get a look at their six-month-old child. Without a thought for the consequences, she carries the baby away. Kiwako then raises the child as her own while being a fugitive from the law.
~~ Adapted from the novel "The Eighth Day" (八日目の蝉) by Mitsuyo Kakuta (角田 光代).