Complex sentence: She starts as an American nurse who moves with her boyfriend to Tokyo after the first nurse Yoko does not show up at work she volunteers to take care of Emma Williams which causes her to fall victim to the curse.
Split into simpler sentences: She starts as an American nurse who moves with her boyfriend to Tokyo. After the first nurse, Yoko, does not show up at work, she volunteers to take care of Emma Williams, which causes her to fall victim to the curse.