Ever since Yuki has accepted her Demi-human nature and started moving on with her life, she's been so much looser, and more open towards building relationships with both her peers and teachers. She would never talk about her problems, but now she's so much more open to everyone around her. For example, she stops by Takahashi-sensei's room, where she even lets him fan her off to help her cool off a bit in the blazing heat. Before her realization, she most likely would have tried to wave it off and deal with it herself, or even try to ignore and push through. But now she lets her guard down and relaxes.
Her relationship with the other Demi-chan students has really improved since their heart to heart. She was so closed off, and kept a barrier between her and all of her peers. Yet here she, able to at least enjoy her time with the other waif- I mean girls. God, and look how cute Machi and Hikari are... I think I have a Demi-chan addiction.
Yuki is also able to physically relax along with emotionally letting go. If you look at her body language and her posture compared to before the episode when she had her breakthrough, there's some slight changes. Whether the animation team put it in on purpose, or if it's just the viewers (me) interpreting it this way, that's up for argument. Although, the animation team has put in a lot of little hints and nudges, such as how it's placed in an actual location. Anyway, if you look at Kusakabe's shoulders, they're slumped down slightly, showing her lack of tension. She's also leaning towards the other girls, making eye contact, and has her knees slightly pointed towards her peers. I don't have any screenshots, but if you look at previous episodes, she positioned herself away from anyone, signalling how she kept herself at a distance.
Also I don't really have anything to say about these last two pictures, I just thought Hikari and Yuki looked super cute in here. Self indulgent? Yes.