Having such a loser as her father makes Mishio feels ashamed of her life. She is not attached to him since she was a child. On top of her disappointment, she decides to move out from house as soon as she graduated.
But, once, her father picked a dolphin and took care of it. The memory lies beneath her and call her love for marine life.
The lesson from this family manga is Gambling is the root of all distrust. You can’t depend on a gambler, because if you do, it makes you a gambler, too.