Apex domains cannot have CNAME records.
Question and response
Question
dig 133.in-addr.arpa. NS
Answer
133.in-addr.arpa. 5 NS g.dns.jp.
133.in-addr.arpa. 5 NS b.dns.jp.
133.in-addr.arpa. 5 NS a.dns.jp.
133.in-addr.arpa. 5 NS d.dns.jp.
133.in-addr.arpa. 5 NS e.dns.jp.
133.in-addr.arpa. 5 NS f.dns.jp.
Authority
The response has no authority records.
Additional
a.dns.jp. 169817 A 203.119.1.1
b.dns.jp. 169817 A 202.12.30.131
d.dns.jp. 169817 A 210.138.175.244
e.dns.jp. 169817 A 192.50.43.53
f.dns.jp. 169817 A 150.100.6.8
g.dns.jp. 169817 A 203.119.40.1
a.dns.jp. 169817 AAAA 2001:dc4:0:0:0:0:0:1
b.dns.jp. 169817 AAAA 2001:dc2:0:0:0:0:0:1
d.dns.jp. 169817 AAAA 2001:240:0:0:0:0:0:53
e.dns.jp. 169817 AAAA 2001:200:c000:0:0:0:0:35
f.dns.jp. 169817 AAAA 2001:2f8:0:100:0:0:0:153
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0