Now we know that Shiro really wasn't trying to make them into weapons. Satan was spying on him the entire time, but what makes this so unfortunate is that Yukio knew and wanted to help him, but Shiro didn't want to shove that kind of responsibility onto him. Might explain Yuki's resentment a little, because he probably could've prevented Shiro's death. Shiro slapped Rin as a shock treatment because Satan was about to possess him during his emotional meltdown (and I highkey hope that Satan doesn't possess him in the next chapter, because Rin is a emotional wreck right now).
Shiro did a good job as a Dad, imo, to say he had no parents, nor examples. He was humbled by so many unfortunate events, but ultimately he just wanted to give the boys a good life. I dunno about anyone else, but the fact that he taught them based on what the boys wanted (Yukio wanted to be strong enough to protect Rin/Rin doesn't wamt Yukio to be afraid of him) rather than force anything upon like we originally thought, really puts me at ease.
I really hope Rin can reach Yukio. What Shiro said about him being kind, generous, and a hardworker, despite his lack of confidence just goes to show you that Yukio isn't a bad person at all. There is good in him, he just can't see it right noe. I'm curious about his lack of appetite. (I need Rin to cook him a meal and for him to cry it out while eating ASAP).