Apex domains cannot have CNAME records.
Question and response
Question
dig 096nikon.237.172.210.in-addr.arpa. NS
Answer
096nikon.237.172.210.in-addr.arpa. 4 NS ns11.sc24.jp.
096nikon.237.172.210.in-addr.arpa. 4 NS ns21.sc24.jp.
Authority
The response has no authority records.
Additional
ns11.sc24.jp. 4 A 203.178.84.118
ns21.sc24.jp. 4 A 203.178.75.166
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0