潜入せんにゅう
sennyū

Noun
Suru Verb

1. infiltration; sneaking in; going undercover

Intransitive
かれ農夫のうふをやつして城下じょうかちょう潜入せんにゅうした。
karewa nōfuni mio yatsushite jōkamachini sennyū shita.
Disguising himself as a peasant, he crept into the castle town.