Apex domains cannot have CNAME records.
Question and response
Question
dig idc.jp. NS
Answer
idc.jp. 5 NS ns02.idc.jp.
idc.jp. 5 NS ns01.idc.jp.
idc.jp. 5 NS ns03.idc.jp.
Authority
The response has no authority records.
Additional
ns01.idc.jp. 5 A 210.158.219.203
ns02.idc.jp. 5 A 64.56.165.91
ns03.idc.jp. 5 A 158.205.198.214
ns01.idc.jp. 5 AAAA 2001:d88:a001:6:210:158:219:203
ns02.idc.jp. 5 AAAA 2001:d88:a001:7:64:56:165:91
ns03.idc.jp. 5 AAAA 2001:d88:a001:8:158:205:198:214
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0