Great Movie - but what's the point? (spoilers)

So Gotetsu was Akari's father. So what was the point of sending her back in time?

1. Since Kazuko was recovering anyway, she could have gone herself, after she got better.

2. Maybe she thought she was dying and hoped Kazuo could save her.

3. Or she thought she was dying and just wanted to prove that she remembered him (in her heart, if not her mind, which I think was her promise).

Until I realized Akari was born Akari Hasegawa, I thought those baby pictures must have been a lost cousin or half-sister. After all, her own baby pictures should have been in color, not B&W, since she was 18 in 2010.

So I mistakenly thought Kazuo must have been her father and her mother must have sent her back so they could meet.

But Gotetsu was her father, so that wasn't the point. I'd have been pretty worried for my kid had I sent one of them back in time. It would have been only for some grand purpose, like saving humanity or the universe or maybe, just maybe, to meet their time-travelling parent, but never just for something sentimental.

I loved the movie though. It must have been the acting, direction, theme, etc. The plot seemed pointless--just a device to show us a theme that fate rules our lives but life goes on...