expression
our conversation; private matter; none of your business
Colloquial phrase used to indicate that the topic is a private conversation or matter, often to dismiss someone's inquiry. Can be used defensively or to set boundaries.
See also: こちらの話
「何の話？」「こっちの話だから気にしないで。」
"What are you talking about?" "It's a private matter, so don't worry about it."
それはこっちの話だ。君には関係ない。
That's our business. It has nothing to do with you.
expression
our side of the story
Used when contrasting one's own version of events with someone else's account, emphasizing that there is another perspective.
彼の言い分だけじゃなくて、こっちの話も聞いてほしい。
I want you to hear our side of the story, not just his version.