Apex domains cannot have CNAME records.
Question and response
Question
dig jp. NS
Answer
jp. 5 NS e.dns.jp.
jp. 5 NS a.dns.jp.
jp. 5 NS c.dns.jp.
jp. 5 NS g.dns.jp.
jp. 5 NS b.dns.jp.
jp. 5 NS f.dns.jp.
jp. 5 NS d.dns.jp.
jp. 5 NS h.dns.jp.
Authority
The response has no authority records.
Additional
a.dns.jp. 159538 A 203.119.1.1
b.dns.jp. 159538 A 202.12.30.131
c.dns.jp. 57263 A 156.154.100.5
d.dns.jp. 172356 A 210.138.175.244
e.dns.jp. 159538 A 192.50.43.53
f.dns.jp. 172301 A 150.100.6.8
g.dns.jp. 159538 A 203.119.40.1
h.dns.jp. 57263 A 161.232.72.25
a.dns.jp. 159538 AAAA 2001:dc4:0:0:0:0:0:1
b.dns.jp. 159538 AAAA 2001:dc2:0:0:0:0:0:1
c.dns.jp. 57263 AAAA 2001:502:ad09:0:0:0:0:5
d.dns.jp. 172356 AAAA 2001:240:0:0:0:0:0:53
e.dns.jp. 159538 AAAA 2001:200:c000:0:0:0:0:35
f.dns.jp. 172301 AAAA 2001:2f8:0:100:0:0:0:153
h.dns.jp. 57263 AAAA 2a01:8840:1bc:0:0:0:0:25
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0