hito no ko ya u wo asobasuru kusa no hana
the man's child
tends to the cormorant...
Or: "cormorants." Japanese fishermen use cormorants. Tied to a tether, these sea birds dive for fish that they are forced to disgorge. The verb asobasuru, which I initially thought had to do with playing, means "attend to" in this context, according to Shinji Ogawa.
The father fisherman let the bird work very hard.
The son of fisherman innocently plays with the bird.
Both belong to human characteristic.