さ (Casual よ)Casual よ

Both can be used to express emotion in casual conversation. The interjection さ is often used at the beginning of sentences and can express encouragement, e.g. さあ、行こう！ ('All right, let's go!'), or hesitation/uncertainty, e.g. さあ、分かりません ('Let's see... I don't know.'). The other usage appears at the end of phrases and functions like a casual よ, e.g. できるさ！ ('You can do it, I'm telling you!').

Both uses of さ are characteristic of casual conversation. The 'casual よ' usage comes at the end of sentences and, like よ, often emphasizes or confirms something to the listener, like 'I'm telling you'. The 'filler' usage of さ appears mid-sentence and ties phrases together, similar to English expressions like 'like' or 'you know', e.g. 昨日さ、ケンジ君に会ったよ ('So yesterday, like, I saw Kenji!').