Apex domains cannot have CNAME records.
Question and response
Question
dig nic.ad.jp. NS
Answer
nic.ad.jp. 4 NS ns3.nic.ad.jp.
nic.ad.jp. 4 NS ns5.nic.ad.jp.
Authority
The response has no authority records.
Additional
ns3.nic.ad.jp. 4 A 202.12.30.163
ns5.nic.ad.jp. 4 A 202.12.30.225
ns3.nic.ad.jp. 4 AAAA 2001:dc2:1000:2000:0:0:0:53
ns5.nic.ad.jp. 4 AAAA 2001:dc2:1000:2000:0:0:0:253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0