A Week of Deserted Island Sex with my Step-Mom [v1.00] [Arukutsuuru]

A passenger ship suddenly encounters a big storm and capsizes.
Miraculously, there are two survivors – a (step)mother and (step)son, who aren’t injured, but are washed ashore and stranded on a deserted island.
The young man rushes to explore the unknown island, attempting to find ways to survive while awaiting rescue.
However, this rare situation gives him the opportunity to be alone with his beloved (step)mother and seduce her.
He uses the innocent game of Rock Paper Scissors to force his initially reluctant (step)mom into lewd acts.
What life choices will the two of them decide upon after a week of being stranded alone on this island?

Emerald_Gladiator thanks for the translation!