Apex domains cannot have CNAME records.
Question and response
Question
dig curumeru.jp. NS
Answer
curumeru.jp. 5 NS ns-573.awsdns-07.net.
curumeru.jp. 5 NS ns-105.awsdns-13.com.
curumeru.jp. 5 NS ns-1597.awsdns-07.co.uk.
curumeru.jp. 5 NS ns-1506.awsdns-60.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0