Apex domains cannot have CNAME records.
Question and response
Question
dig fastcloud.jp. NS
Answer
fastcloud.jp. 5 NS ns-772.awsdns-32.net.
fastcloud.jp. 5 NS ns-479.awsdns-59.com.
fastcloud.jp. 5 NS ns-1987.awsdns-56.co.uk.
fastcloud.jp. 5 NS ns-1289.awsdns-33.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0