Apex domains cannot have CNAME records.
Question and response
Question
dig fujitsu.co.jp. NS
Answer
fujitsu.co.jp. 5 NS a4-67.akam.net.
fujitsu.co.jp. 5 NS a5-64.akam.net.
fujitsu.co.jp. 5 NS a1-171.akam.net.
fujitsu.co.jp. 5 NS a10-64.akam.net.
fujitsu.co.jp. 5 NS a22-65.akam.net.
fujitsu.co.jp. 5 NS a3-66.akam.net.
Authority
The response has no authority records.
Additional
a4-67.akam.net. 5 A 72.246.46.67
a4-67.akam.net. 5 AAAA 2600:1480:9000:0:0:0:0:43
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0