Sachiko was a lady-in-waiting or housemaid to Heiko.
When Heiko died after giving birth to Makoto, Sachiko and Matthew became his foster parents. The elder Starks allowed Makoto to think he was their biological child.
Sachiko argued with Matthew after Makoto was found to be the "Chinatown Bandit" but acquiesced to Makoto being sent to Canada until interest in the bandit had abated. She last saw Makoto when he left for the train station with Jiro.