Apex domains cannot have CNAME records.
Question and response
Question
dig repica.jp. NS
Answer
repica.jp. 5 NS ns-1836.awsdns-37.co.uk.
repica.jp. 5 NS ns-1331.awsdns-38.org.
repica.jp. 5 NS ns-329.awsdns-41.com.
repica.jp. 5 NS ns-729.awsdns-27.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0