Apex domains cannot have CNAME records.
Question and response
Question
dig kddi.ne.jp. NS
Answer
kddi.ne.jp. 5 NS dns0.dion.ne.jp.
kddi.ne.jp. 5 NS dnsa01.kddi.ne.jp.
kddi.ne.jp. 5 NS dns1.dion.ne.jp.
kddi.ne.jp. 5 NS dnsa02.kddi.ne.jp.
Authority
The response has no authority records.
Additional
dns0.dion.ne.jp. 5 A 210.141.108.194
dnsa01.kddi.ne.jp. 5 A 54.64.39.199
dnsa02.kddi.ne.jp. 5 A 54.92.27.113
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0