For specific 2020 data, your best bet is likely professional data providers like who sold such lists, but for current ongoing needs, an active sourcing strategy is essential.
"合同会社" "@yahoo.co.jp" "大阪" (Targets limited liability companies in Osaka using Yahoo Japan). For specific 2020 data, your best bet is
Sending unsolicited commercial emails (cold emailing) to individuals is generally restricted. You must have prior consent from the recipient to send advertisements or promotional material. For specific 2020 data
Despite the corporate preference for custom domains, webmail providers play a specific role in the Japanese market: but for current ongoing needs