Apex domains cannot have CNAME records.
Question and response
Question
dig mind.ad.jp. NS
Answer
mind.ad.jp. 5 NS tokio.mind.ad.jp.
mind.ad.jp. 5 NS ns.mind.ad.jp.
mind.ad.jp. 5 NS ns2.mind.ad.jp.
Authority
The response has no authority records.
Additional
ns.mind.ad.jp. 5 A 202.228.1.35
ns2.mind.ad.jp. 5 A 202.228.1.81
tokio.mind.ad.jp. 5 A 202.228.1.36
ns.mind.ad.jp. 5 AAAA 2001:358:31:101:0:0:0:310c
tokio.mind.ad.jp. 5 AAAA 2001:358:31:101:0:0:0:310d
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0