は vs が ( Wa vs Ga )

は and が is Japanese particles and they are used for Subjective. Wa and Ga are very similar. Basically you can use は wa for subjective like “さとうさんはにんじゃです” .  If you want to emphasize the subjective you better to use がga.

Lesson : Wa vs Ga

A「さとうさんはにんじゃです。」

Satou san is Ninja.

B「え？だれがにんじゃですか？」

Ehh? Who is Ninja?

A「かれがにんじゃです。」

He is Ninja.