Apex domains cannot have CNAME records.
Question and response
Question
dig mirae.co.kr. NS
Answer
mirae.co.kr. 5 NS ns.mirae.co.kr.
Authority
The response has no authority records.
Additional
ns.mirae.co.kr. 5 A 203.251.24.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0