Apex domains cannot have CNAME records.
Question and response
Question
dig inetidc.jp. NS
Answer
inetidc.jp. 5 NS ns2.inetidc.jp.
inetidc.jp. 5 NS ns3.inetidc.jp.
inetidc.jp. 5 NS ns1.inetidc.jp.
Authority
The response has no authority records.
Additional
ns1.inetidc.jp. 5 A 61.196.168.229
ns2.inetidc.jp. 5 A 61.196.169.5
ns3.inetidc.jp. 5 A 210.191.83.176
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0