So the father is actually him going in the past?

no, based on what we've seen so far, the current Gunji Akira at some point in the near future will somehow transport back to the past during the battle where his own father dies and Sho and his sister were attacked by the big wolf/fox alien and be spotted by Amamiya Reiji who was also severely injured.

I know, I was just theorizing, though it does seem far fetched