netblock.oneoffice.jp has no CNAME records.
Question and response
Question
dig netblock.oneoffice.jp. NS
Answer
The response has no answer records.
Authority
oneoffice.jp. 431 SOA dns1.broadline.ne.jp. dns-info.broadline.ne.jp. 668 10800 900 604800 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0