Apex domains cannot have CNAME records.
Question and response
Question
dig web.ad.jp. NS
Answer
web.ad.jp. 5 NS ns3.hyper.web.ad.jp.
web.ad.jp. 5 NS ns.web.ad.jp.
web.ad.jp. 5 NS ns1.hyper.web.ad.jp.
web.ad.jp. 5 NS ns2.web.ad.jp.
web.ad.jp. 5 NS ns2.hyper.web.ad.jp.
web.ad.jp. 5 NS ns3.web.ad.jp.
Authority
The response has no authority records.
Additional
ns.web.ad.jp. 5 A 202.248.2.201
ns1.hyper.web.ad.jp. 5 A 202.248.0.3
ns2.web.ad.jp. 5 A 202.219.177.121
ns2.hyper.web.ad.jp. 5 A 202.248.0.59
ns3.web.ad.jp. 5 A 210.131.113.123
ns3.hyper.web.ad.jp. 5 A 210.131.113.124
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0