Apex domains cannot have CNAME records.
Question and response
Question
dig topica.ne.jp. NS
Answer
topica.ne.jp. 5 NS ns020-bda94cj0mg0l6j25.b.d-53.jp.
topica.ne.jp. 5 NS ns020-bda94cj0mg0l6j25.b.d-53.info.
topica.ne.jp. 5 NS ns020-bda94cj0mg0l6j25.b.d-53.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0