According to former US and Japanese officials, the NSA discovered in the fall of 2020 that the PRC had persistent access to Japanese Defense Networks.
This prompted a bilateral engagement to enhance Japanese Network security.
Kind of scary to think about all the state hacking going on that hasn’t yet been revealed.
https://www.theguardian.com/world/2018/nov/15/japan-cyber-security-ministernever-used-computer-yoshitaka-sakurada
I think this article is enlightening on Japan’s cybersecurity. Things may have changed but people like this being in charge put them way behind.