I tried to write a haiku

This is more a joke than anything, but I wrote a haiku in response to the quiz saying that there is less than 1 island in Japan. It is phonetically something like this:

ma-chi-ga-i
shi-ma no se-tsu-na wa
ik-ka-i na-i

In English it's something like this:

mistake

an island’s moment

not once

I don't know if this is correct in any way. I also don't know if conventionally the subject of one line can be maintained to the next.