The maximum foreign equity share in accounting and auditing firms is under 50%. An invidivual foreign investor accountant may only hold a less than 10% equity share. Only (domestic or foreign) certified public accountants may be shareholders.
"Article 40-12 (Investment in Accounting Corporations) Foreign certified public accountants may invest in an accounting corporation established pursuant to Article 23 within the scope of less than 50/100 of investment share with a voting right or total amount of capital of the relevant accounting corporation. In such cases, the upper limit of the amount of investment per foreign certified public accountant shall be less than 10/100 of investment share with a voting right or total amount of capital of the relevant accounting corporation.[...]" (Certified Public Accountant Act (No. 1797 of 1966), last amended by Act No. 18114 of 2021, Article 40-12 [unofficial translation]) 
Certified Public Accountant Act (No. 1797 of 1966), last amended by Act No. 18114 of 2021, Article 40-12
[<a href="https://www.law.go.kr/LSW/lsEfInfoP.do?lsiSeq=198537#">Act</a>],[<a href="https://www.law.go.kr/LSW/eng/engLsSc.do?menuId=2&section=lawNm&query=certified+public+accountant+act&x=0&y=0#liBgcolor0">Act_Eng</a>]