Final answer:
Sachiko is experiencing technology addiction, which is an excessive and compulsive use of technology that interferes with daily life and functioning.
Step-by-step explanation:
Sachiko is experiencing a form of technology addiction. Technology addiction refers to an excessive and compulsive use of technology, such as smartphones, that interferes with a person's daily life and functioning. In this case, Sachiko's refusal to silence her phone at night and her constant checking of it, even during sleep, indicates a dependence on technology that is negatively impacting her sleep and overall well-being.