As a general rule, businesses that employ workers are covered by employment insurance.The website of the Ministry of Health, Labor and Welfare shows what kind of quarantine measures will be taken when entering Japan.

Businesses that employ even one worker, whether corporations or solely businesses, are covered by employment insurance, with the exception of some of the agriculture, forestry and fisheries industry.
If you become an employment insurance-covered business, you will need to follow the steps below.
1) Submit a "Notice of Success in Labor Insurance Relations" to the Labor Standards Inspection Office.
2) Submit a notification to the public employment security office to establish a "Employment Insurance Covered Business Employment."

For more information, please visit the Ministry of Health, Labor and Welfare's website below.
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/koyou_roudou/koyou/jigyounushi/page15.html