Write a short story where the protagonist has a doppelganger. #doppelganger

Anna is a simple woman living in a simple house, and she lives alone. One day, Anna's friend Mika visited her. Mika knocked on Anna's door, but no one opened it. She tried knocking several times, but there was no response and no sign of Anna.

Mika decided to enter Anna's house, thinking Anna might be asleep. Mika called out for Anna, but there was still no response. After a while, Mika heard...