The Travel Rule is a regulation promoted to be introduced globally by the Financial Action Task Force (FATF), an international body that sets standards for combating financial crimes. It aims to enable the tracing of crypto asset transaction paths. Under this regulation, crypto asset exchange operators and financial institutions located in jurisdictions subject to the notification requirements are required to transmit information on both the sender and recipient at the time of a crypto asset transfer. The purpose is to prevent misuse of crypto assets for illicit activities such as money laundering and terrorist financing.
More information can be found here(only available in Japanese).
Please also read the announcement from the Japan Virtual and Crypto asset Exchange Association (JVCEA) (only available in Japanese).