忍者

1. Origins, structure, and basic meaning

• Structure: 忍者 is read as にんじゃ and is a noun for a ninja associated with covert action and infiltration in Japanese history and narrative.
• Basic usage: Use 忍者の衣装 for a costume and 忍者が城へ忍び込む for a character entering a castle covertly.

2. Common pitfalls and similar expressions

• Costume and role
  • The younger brother is dressed as a ninja at a festival, while the story presents a ninja character carrying out an infiltration.
• Manner and destination
  • 音を立てずに describes moving without noise, and 城へ marks the destination entered secretly.