As the instructions are in Japanese I will re-create them here.
You have to get all the characters across the river.
The boat can only hold two characters at a time.
Only the mum, dad, or the policeman can drive the boat.
You can't leave either little girl alone with the dad without the mum.
You can't leave either little boy alone with the mum without the dad.
You can't leave the criminal alone with any member of the family without the cop.