Apex domains cannot have CNAME records.
Question and response
Question
dig datahotel.co.jp. NS
Answer
datahotel.co.jp. 5 NS zns01.datahotel.ne.jp.
datahotel.co.jp. 5 NS zns02.datahotel.ne.jp.
Authority
The response has no authority records.
Additional
zns01.datahotel.ne.jp. 5 A 203.174.65.4
zns02.datahotel.ne.jp. 5 A 203.174.65.68
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0