If we take movie!Touga's traumatic background and apply it to that particular sequence then you cannot help but wonder if Touga was reading some abuse into the story. And not pertaining to the cat at all but concerning Nanami. That first screenshot, with the faceless shadow figure holding Nanami does not in itself hint at pedophilia but if Touga was a victim of sexual assault at a young age and by the same person then it is very likely that he would view things in such a light.
And if so it gives a whole different meaning as to what the 'rescue' really was all about.

Yeah, it's almost suspect as a sequence. He intervenes on her behalf but he has a rather smirky little expression, like he enjoys the situation. Maybe he gets a thrill also out of overriding his father in a setting where he'd look especially douchey pressing the issue.

If we go with his father as sexually abusive, which I certainly do, it also throws several meanings on the sequence. One, like I said above, because it's public, his birthday, etc, this was a rare chance for Touga to rebel in a way no one would be justified in faulting him for.

It also involves him stopping his father from doing something to Nanami, and might therefore mirror one of the things about his being abused by his father. There is a perverse, sadly adult way about Touga's idea of protection, and he strikes me as someone that would choose to draw his father's attention, sexual or anger or whatever else, as a way to protect Nanami.

The more I think about it, the more I wonder if this sequence/story in some way is telling us that Nanami is aware of that. She's chosen the kitty story to pin it on, because I think she was probably far too young to really grasp exactly what was happening. But somewhere, on some level, she knows her brother has protected her in some vital way. That kind of attachment, that she has, to a sibling, is not a given. There's a reason and a connection there that's a lot deeper than 'he liked my dirty kitten that made dad mad.'

Really if you didn't know the context, that set of pictures looks a lot more like he's stopping someone from sexually assaulting her. If your miserable brat kid had done that and you were angry, would you approach from behind and around? No, you'd probably pull back their shoulder to grab the box or something. It's just very suspect.