Hmmm, so even though they aren't all the immortal planet or whatever anymore, technically wouldn't Kagura and Komui be half of whatever species their mom and Gintoki's teacher are? Guess you can't really be half immortal though I mean you either are are aren't.
I think maybe Kamui abandoned Kagura because at some point, he came to believe that to be strong means you have to cast aside weaknesses (or weak ppl) just a theory. I thought it was cool how Abuto told him to take care of Kagura otherwise he'll become a villain and Abuto and Kamui's whole relationship is interesting.