Can から mean それでは?

Question

A: もう用がねぇなら帰るけど

B: 用がないわけじゃないけど 今日はなんかタイミングがよくない

A: じゃあ帰るからな

I would like to know if kara is used commonly in Japanese to say also "in that case" (besides of "because"), or is it used as a softener or for another reason in this context?

Thank you so much in advance!

Answer 1

According to 明鏡国語辞典:

から 🈔〘接続助詞〙
❻《文末に用いて》注意・警告・慰めなどの気持ちを表す。
「先生に言いつけてやるから。」「私もう帰るから。」「心配しなくていいから。」

The conjunctive particle から at the end of a sentence can express a feeling of 注意・警告・慰め (cautioning, warning, comforting/cheering up). Here in your context the から is not "because" or "so", but expresses soft/mild 注意 or 警告, adding a nuance of "~~, alright? / okay? / you see?" etc. It is daily used in real life as in 「じゃ、(もう)帰るから(ね)。」「じゃ、(もう)行くから(ね)。」 etc. to mean "Well/Okay, I'm going home / leaving now (, alright?)"

Answer 2

In this case, as you mentioned, から is a softener, for making the parting of ways not so harsh.

Without the から: a bit cold

じゃあ帰る

Alright, I'm going home.

With the から: adds the sense of "if there's anything else you want to talk about, please bring it up now, because I plan to go home now."

じゃあ帰るから（他に話すことがあるなら今話そうね。なければ、また会いましょう。）

Alright, I'm going home, so...(if there's anything else you want to talk about, please bring it up now, because I plan to go home now.)

EDIT (additional comment): Generally, the meaning of the "elliptical" から can vary depending on situation.

A different example from the one above:

もう、帰るから！

I'm leaving! (...so don't talk to me, because I'm angry, frustrated, etc.)