Apex domains cannot have CNAME records.
Question and response
Question
dig volleyball.ne.jp. NS
Answer
volleyball.ne.jp. 5 NS ns-tk022.ocn.ad.jp.
volleyball.ne.jp. 5 NS ns.volleyball.ne.jp.
Authority
The response has no authority records.
Additional
ns.volleyball.ne.jp. 5 A 210.232.102.50
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0