A.
If the message "You will need to set up an email address in order to set up your identity verification. Please ask the person who registered your Expo ID on your behalf to set up an email address for you." is displayed, you need to ask the person who registered your proxy to register an additional email address.
https://www.expo2025.or.jp/wp/wp-content/themes/expo2025orjp_2022/assets/pdf/tickets-index/id_registration_manual_en.pdf
https://www.expo2025.or.jp/wp/wp-content/themes/expo2025orjp_2022/assets/pdf/tickets-index/id_registration_manual_en.pdf