根城 ねじろ
nejiro

Noun

1. stronghold; citadel

泥棒 どろぼう、間違 まちがいなくここにいるはずよ。きっと、どこかに根城 ねじろがあるから、そこを つけさえすればいいの。
dorobōwa machigainaku kokoni iru hazuyo. kitto dokokani nejiroga arukara sokō mitsukesae sureba iino.
The thief has to be in here. I'm sure somewhere around is his stronghold so if we can just find that we've got him.
Noun

2. base (of operations); headquarters