Learn in the textbookInternational and Adjacent Personal Data Laws — My Number Act and GDPR
DefinitionThe My Number Act (マイナンバー法) is the law that sets where the 12-digit Individual Number (個人番号, known as My Number) given to each resident may be used and how it must be kept safe.
ExplanationIts formal name is the Act on the Use of Numbers to Identify a Specific Individual in Administrative Procedures, and personal information containing an Individual Number is called specific personal information (特定個人情報). The number may be used only for tasks the law lists, such as social security, tax, and disaster response procedures, and as a rule it cannot be used for anything else even with the person's consent. A business that receives someone's number must also verify that person's identity.
AnalogyThink of it as a spare key made only for government paperwork. It fits only the designated doors (procedures set by law), and you are not allowed to use it to open any other door.
Memory hook"My" + "Number": the law about a number that belongs to me alone. The phrase "use of numbers" in the formal name shows that the law centers on how the number is used.