Apex domains cannot have CNAME records.
Question and response
Question
dig ymir.co.jp. NS
Answer
ymir.co.jp. 5 NS dns1.ymir.co.jp.
ymir.co.jp. 5 NS ns2k.ymir.co.jp.
Authority
The response has no authority records.
Additional
dns1.ymir.co.jp. 5 A 59.106.32.195
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0