Apex domains cannot have CNAME records.
Question and response
Question
dig 0.158.223.194.in-addr.arpa. NS
Answer
0.158.223.194.in-addr.arpa. 5 NS dns1.ymir.co.jp.
0.158.223.194.in-addr.arpa. 5 NS dns2.ymir.co.jp.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0