"Painful" vs. "hurtful"

Painful is much more appropriate than hurtful in your example sentence.

Hurtful carries a strong connotation that the hurt is deliberate, or at least callous. Painful doesn’t carry this connotation at all. Also, hurtful is mostly reserved for emotional or psychological pain, while painful can refer either to emotional or physical pain.

For instance, if someone makes a crude joke about cancer, that could be both hurtful and painful. If someone gives a eulogy that vividly brings back memories of a departed friend, that might be painful for the listeners, but not hurtful.

In common usage, "hurtful" has the connotation of the thing being referred to as intending to cause pain, rather than causing pain as an effect, where "painful" would be more likely to be used.

From your context, it sounds as if "hurtful" would probably not be the best word choice, unless the story of the fish, perhaps, was an allegorical story intended to point out the listener's character faults.

For example, the Shakespeare play Hamlet could be considered painful, as it might cause sadness in the audience. However, the virtually identical play-within-the-play that is presented to the new king was hurtful, as it was intended to shame the king.

The recipient of a hurtful action would be "hurt". The recipient of a painful action would be "in pain" (or less commonly, "pained"), but that really implies physical pain, not emotional. You'd probably use a more specific word, like "saddnened", "sad" or "angry".

"It was hurtful when he called me a jerk. He hurt me. I was hurt."

"It was painful when I realized I was a jerk. The realization saddened me. I was sad."