Apex domains cannot have CNAME records.
Question and response
Question
dig tnc.ne.jp. NS
Answer
tnc.ne.jp. 5 NS dns2.tokai.or.jp.
tnc.ne.jp. 5 NS dns1.tokai.or.jp.
Authority
The response has no authority records.
Additional
dns1.tokai.or.jp. 5 A 42.127.238.230
dns2.tokai.or.jp. 5 A 211.7.91.38
dns1.tokai.or.jp. 5 AAAA 2403:7800:5021:102:0:0:0:230
dns2.tokai.or.jp. 5 AAAA 2403:7800:5021:202:0:0:0:38
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0