hi! sorry i didn't see this for so long, but i think his relationship with the kids is a little more stand off ish than suguru's both due to work and his own personality. they're still super close which can especially be seen when satoru had a one on one outing with tsumiki, but he just has a different style of parenting. it doesn't help that he doesn't see himself as being very good at emotions like suguru is. he's better than he thinks, but in the grand scheme of things, his relationship with the kids would shine best when they're teenagers and he can help them grow/stand on their own, which i personally think compliments suguru really being best when the kids are younger and need to be dependent on them. but that's just my take on it (i'm aware i'm the author but that will be outside the scope of even the completed story/my personal interpretations on the two even as their canon characters) regardless, he does really love them and they feel the same about him.