Sneaking in or infiltrating: entering a place covertly so as not to be noticed; often used in contexts like espionage, investigations, or crimes.
捜査官が夜中に建物に潜入して証拠を集めた。
An investigator snuck into the building at night and collected evidence.
泥棒が倉庫に潜入して貴重品を盗んだ。
A thief infiltrated the warehouse and stole valuables.
スパイ映画では敵地に潜入する場面がよく出てくる。
Spy movies often feature scenes of infiltrating enemy territory.