Apex domains cannot have CNAME records.
Question and response
Question
dig 128.220.127.219.in-addr.arpa. NS
Answer
128.220.127.219.in-addr.arpa. 4 NS ns3.ambisys.jp.
128.220.127.219.in-addr.arpa. 4 NS ns1.ambisys.jp.
Authority
The response has no authority records.
Additional
ns1.ambisys.jp. 4 A 210.175.226.118
ns3.ambisys.jp. 4 A 61.215.192.140
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0