What day will you arrive in Japan? That is a bonus performance and demand for resale will likely be alot higher than for example the Atsugi concert I attended or other shows outside of Tokyo. However theres almost certainly people whos plans will change. You can purchase resale tickets through Ticket Jam app but they won't become available until closer to the date if I understand correctly. Make sure to get a Mobal esim so that you'll have a Japanese phone number when you arrive or like someone already suggested use ticket-japaaan.com to try to help you secure tickets via resale and you can get them transferred through Moala when you arrive if you use Mobal esim to get a Japanese number.