Hajime Hinata:
Any affection he gets makes him feel warm and fuzzy inside. He does try to return any affection that is given to him. Having an affectionate darling will make him more attached to them.
Izuru Kamukura:
He doesn't really feel one way or the other about it. Although when his darling does show affection to him there's this odd familiar feeling that he gets. He's not too sure what it is but he knows that he doesn't want it to go away.
Nagito Komaeda:
A bit conflicted about having such a sweet darling. On one hand he loves Every second of it but on the other hand he doesn't think they should be that loving to him. Although he never tells them to stop what they are doing, he does sometimes falls into old habits of saying that he doesn't deserve all this love. (That and the fact that he knows they would hate him if they know just some of the things he had done.
Gundham Tanaka:
Adorable them even more and (if even possible.) Falls even deeper in love. Having an affectionate darling may actually calm down his yandere ways but it will also make some parts stronger. Like his possessive side and protective side, it may also led to him kidnapping a lot sooner.
Kazuichi Soda:
An affectionate darling is the perfect darling for kazuichi. In return for all the love his darling shows him he will return it tenfold and become even more clingy. He will also become more determined not to let them leave him.
Teruteru Hanamura:
His yandere side does calm down quite a bit with an affectionate darling. Although just like some of the others, some other parts start to show more. Like being possessive and wanting his darling's attention on him.
Nekomaru Nidai:
Having such a sweet darlings feeds into his delusion making everything even more normal to him. He does become jealous if his darling is showing any type of affection to anyone else, friendly or not. He also becomes much more possessive over this type of darling.
Fuyuhiko Kuzuryu:
It's a weird mix of seeming like he hates it and taking pride in it. This shows that he has won their heart (even if they meant things in a friendly manner.) The only reason why he seems like he hates it is because of the front he has to put up but in true he melts any time they show him some love.
Byakuya Twogami/ Ultimate Imposter:
They melt Every time their darling shows them any amount of affection. They do return it in full feeling like they truly win their darling over. All in all, they are happy that their darling doesn't hate them.
Akane Owari:
She became so soft and mushy when her darling gave her any type of affection. She will not only return it tenfold but become even clinger then she already was. However, she will also start to want more each time. (More kisses, sweet words etc.)
Chiaki Nanami:
Soft, everything comes so soft between Chiaki and her darling. It's almost like they are in a normal relationship. All in all, out of all of the others she is the one that will make things seem more normal.
Sonia Nevermind:
She adores her darling and the fact that they are willingly giving her love just makes things much easier. She loves it if they were to show affection in public so people can see that they are together. An affection also reinforces her delusions which depending on her darling's next move could make things more...dicey.
Hiyoko Saionji:
She tries so hard to act like she hates any affection her darling gives her but in truth she wants nothing more than her darling being sweet to her.
Ibuki Mioda:
Ibuki and her daring just become a mess of lovey doveyness. Both look like just another clingy and mushy couple. Although if someone says something negative about it then they won't be there the next day.
Mahiru Koizumi:
It's the perfect darling for her and it makes things much easier. Like someone of others she will become much more possessive of this type of darling but they also calm down her yandere side. So, all in all it's a win win for everyone.
Mikan Tsumiki:
It's most likely why she is a yandere for them in the first place. Any time her darling shows her affection she's in heaven. There's also a greater chance of her kidnapping this type of darling.
Peko Pekoyama:
She will return her darling's affection as best she can although it usually just ends up with her doing something for them. Like getting rid of people who she believes will harm them or just stay even closer to them then she already does.