it's a long story

Phrase

The situation is too complicated or extensive to talk about. / The situation is too embarrassing to talk about.

Japanese Meaning

事情が複雑で一言で説明できない / 話すには恥ずかしい、または長ったらしくなってしまう状況

I wanted to tell you why I left, but it's a long story.

なぜ私が辞めたのか伝えたかったのですが、説明するには複雑すぎます。

Sense（1）

The situation is too complicated or extensive to talk about.

Sense（2）

The situation is too embarrassing to talk about.