Apex domains cannot have CNAME records.
Question and response
Question
dig 233.238.202.static.iijgio.jp. NS
Answer
233.238.202.static.iijgio.jp. 4 NS ns01.iij-dns.jp.
233.238.202.static.iijgio.jp. 4 NS ns00.iij-dns.net.
Authority
The response has no authority records.
Additional
ns00.iij-dns.net. 2 A 210.138.20.112
ns01.iij-dns.jp. 2 A 202.32.219.52
ns00.iij-dns.net. 2 AAAA 2001:240:bb81:0:0:0:29:112
ns01.iij-dns.jp. 2 AAAA 2001:240:bb81:0:0:0:28:52
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0