Apex domains cannot have CNAME records.
Question and response
Question
dig infoweb.ne.jp. NS
Answer
infoweb.ne.jp. 4 NS ns.web.ad.jp.
infoweb.ne.jp. 4 NS ns3.web.ad.jp.
infoweb.ne.jp. 4 NS ns2.web.ad.jp.
Authority
The response has no authority records.
Additional
ns.web.ad.jp. 4 A 202.248.2.201
ns2.web.ad.jp. 4 A 202.219.177.121
ns3.web.ad.jp. 4 A 210.131.113.123
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0