dolphin.kddnet.ad.jp has no NS records.
NS records for this zone are defined at kddnet.ad.jp.
NS records for this zone are defined at kddnet.ad.jp.
Question and response
Question
dig dolphin.kddnet.ad.jp. NS
Answer
The response has no answer records.
Authority
kddnet.ad.jp. 300 SOA penguin.kddnet.ad.jp. sysadmin.noc.kddnet.ad.jp. 2017061901 600 180 3600000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0