This visa category is for those who wish to study Korean at a university language education center or at educational institutions or organizations other than organizations under the D-2 status described already. Students who are planning to study for more than one term (more than 91 days) should apply for D-4 visa. This visa is usually valid for 6 months and can be renewed within Korea. Since this visa takes approximately 1 month to be processed, students should apply for this visa at least 2 months before leaving for Korea.
※ If necessary, the chief of a Korean Embassy or Consulate may ask an applicant to submit additional documents not listed below.
① Passport
② Application for Visa Issuance (available at Korean Embassy or Consulate)
③ Certificate of Admission
④ Certificate of tuition payment
⑤ a copy of business registration or copy of school registration
⑥ Certificate of graduation or certificate of enrollment
⑦ Certificate of bank balance (more than US$ 3,000) or certificate of remittance or exchange
⑧ 1 color ID photo (3.5cm x 4.5cm)
  - photos must have been taken within the past 6 months
  - printed photos are not accepted.
  - background of the photo must be white
⑨ Fee (single-entry visa: US$50, multiple-entry visa: US$80)
⑩ Notarized Sponsorship Letter
⑪ For Chinese only, a copy of Chinese ID card and Hogubu(list of all family members)
[From Hi Korea website (http://www.hikorea.go.kr)]