が、実際は

but in reality

→ が
phrase Rare #40,893
but in reality Used to contrast an expectation, belief, or assumption with what is actually true. The が means “but,” while 実際は means “in reality” or “actually.”
JA: 簡単だと思ったが、実際はとても難しかった。
EN: I thought it would be easy, but in reality it was very difficult.

彼は何でも知っていると思っているが、実際はひどく無知である

He thinks he knows everything, but in reality, he’s terribly ignorant.

彼は君を好きだと思っていたが、実際はほかの女の子が好きだったのだ

I thought he liked you, but actually, he liked another girl.

彼女は役に立つと私は思ったのだが、実際はいない方がよかったのだ

I thought she would be useful, but as it turned out, it would have been better if she hadn't been there.

事態はよくなる期待していたが、実際はますます悪化している

I had hoped the situation would improve, but in reality, it’s only getting worse.