If a person wishes to enter and stay in Japan for more than 3 months with a specific purpose, they must apply for a Certificate of Eligibility (COE).
COE is necessary for someone who will be working or studying in Japan, or maybe living with their family. Applicant must have a guarantor in Japan like a Spouse, relative, company, or school.
Guarantor applies the Certificate of Eligibility for the person they want to summon from abroad.
For example, a company will be the one to apply the COE for the employee they are hiring from the Philippines.
Once they obtain the Certificate of Eligibility. They have to send it to the applicant, so they can apply there visa wherever they are. The applicant must go to a Japan Embassy or Consulate to send their application of visa with COE.
For additional information, the requirements for applying for Certificate of Eligibility differs for each purpose.
Please visit this website to know what supporting documents you need to provide for your application.