Ticket IDs purchased from travel agencies and other vendors, or ticket IDs obtained from sources other than this site, can be added to your "My Tickets" by performing "Additional Ticket Registration".
When registering for an additional ticket, enter the "Ticket ID" of the ticket to be added on the registration screen. You can register up to 10 additional tickets at the same time. Please note that the following tickets cannot be registered.
・Used tickets
・Tickets that have already been added to another person's My Ticket
・Tickets that have become unusable for some reason

https://ticket.expo2025.or.jp/en/faq/