Apex domains cannot have CNAME records.
Question and response
Question
dig jpne.co.jp. NS
Answer
jpne.co.jp. 1 NS ns4.jpne.co.jp.
jpne.co.jp. 1 NS ns1.jpne.co.jp.
jpne.co.jp. 1 NS ns2.jpne.co.jp.
jpne.co.jp. 1 NS ns3.jpne.co.jp.
Authority
The response has no authority records.
Additional
ns1.jpne.co.jp. 1 A 27.86.3.49
ns2.jpne.co.jp. 1 A 175.130.241.33
ns3.jpne.co.jp. 1 A 106.153.224.128
ns4.jpne.co.jp. 1 A 106.153.224.192
ns1.jpne.co.jp. 1 AAAA 2001:268:fa04:149:0:0:0:1
ns2.jpne.co.jp. 1 AAAA 2001:268:fa30:d49:0:0:0:1
ns3.jpne.co.jp. 1 AAAA 2001:268:fa04:a41:0:0:0:1
ns4.jpne.co.jp. 1 AAAA 2001:268:fa30:2241:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0