This visa category is designed for students who seek to earn a degree (bachelor's or higher) or conduct a specific study at a college, university / graduate school set up under a provision of the Education Law or at the educational facilities set up under a provision of the special law. Exchange students must apply for D-2 visa before entering Korea.
The D-2 visa holder is not allowed to engage in activities for remuneration such as a part-time job. In the case that a foreign student breaks this rule, he/she will be penalized according to the article 94 or 95 of Immigration Law. In principle, the tuition fee or living expenses in Korea shall be covered by his/her own money, therefore, an applicant who intends to earn money for tuition fees or expenses in Korea is restricted from this visa issuance.
※ 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 Letter of Acceptance (issued by Sogang University)
④ Certificate of Admission (issued by Sogang University)
⑤ Certificate of the latest scholastic achievement
⑥ Certificate of bank balance (1 semester: more than US$ 6,000. 2 semesters: more than US$ 10,000)
⑦ Letter of Sponsorship
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 Census registry (applicable to Chinese students only - all family members must be listed)

[From Hi Korea website (http://www.hikorea.go.kr)]