Apex domains cannot have CNAME records.
Question and response
Question
dig bit-drive.ne.jp. NS
Answer
bit-drive.ne.jp. 1 NS dns02.bit-drive.ne.jp.
bit-drive.ne.jp. 1 NS dns01.bit-drive.ne.jp.
Authority
The response has no authority records.
Additional
dns01.bit-drive.ne.jp. 1 A 211.9.32.196
dns02.bit-drive.ne.jp. 1 A 211.9.32.227
dns01.bit-drive.ne.jp. 1 AAAA 2001:298:402:101:0:0:0:196
dns02.bit-drive.ne.jp. 1 AAAA 2001:298:402:102:0:0:0:227
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0