Apex domains cannot have CNAME records.
Question and response
Question
dig activegate-ss.jp. NS
Answer
activegate-ss.jp. 5 NS ns-1269.awsdns-30.org.
activegate-ss.jp. 5 NS ns-25.awsdns-03.com.
activegate-ss.jp. 5 NS ns-830.awsdns-39.net.
activegate-ss.jp. 5 NS ns-2033.awsdns-62.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0