Well, I'm just gonna say this, I LOVE THE IDEA OF MAFUYU DOUBLE and I also agree that Cat is the most catchy Milgram song so if someone is going to cover Cat then it has to be the best out of there!
Personally I'd switch Kohane and Nene because I think that Kohane really fits the more faster vibe of "It's not my fault" and "After Pain" just sounds like a Nene song idk. But other then that, it all fits perfectly
This is the most correct video about project sekai milgram that I have seen. (I also think "It's Not My Fault" fits Nene for her tendency to blame Tsukasa a lot or make fun of him when it's not really his fault and Triage/any Shido song for that matter fits Kanade as Kanade has dealt with two family incidents but ignores her pain to keep trying to save people like how Shido kept trying to do more heart transplants even though they kept ending in failure.) Some insight on why Mafuyu could fit Double is Mafuyu kinda has a "split personality" with her good girl persona and her empty true personality.
If I see ONE person go "Fuuta's the third shinonome sibling!!!!! :))))" I swear on my momma I'm gonna come to ur house in game and I'm not do anything bc I'd rather not interact tyyyy