The slow progression of the new relationship of Bossun and Tsubaki, after they find out that they are twin brothers, and how they start getting more and more along with each other:
One day, Akane invites Tsubaki to eat dinner with them, as she wanted to meet the other child of her best friends, Ryosuke and Haru Kirishima. She even remarks that while Bossun looks more like Ryosuke, Tsubaki looks similar to Haru, as he shares the same eyelashes from her. When the twins are watching Ryosuke's home movies, Tsubaki cries out of happiness as he is very glad that he met his biological parents through them. They eat dinner together and share the same table, and then they finally take a picture together. They might be standing with a distance between them, but they are taking baby steps.
When Tsubaki wants to defend Daisy from some blackmailers, he asks Bossun for some advice about the situation. And even if he wanted to do it for himself, the Sket Dan helps him afterwards (they go as "unwanted" back ups, poorly disguised, but they were a necessary help).
Tsubaki admits little by little that Bossun is becoming a greater influence on his life, such as that time he wanted to do coordinated t-shirts for him and the rest of the Student Council.
And how about the time they ended up teaming up in a JRPG?
Any time when Switch shows that he really cares about Reiko, despite their different arguments about Occultism vs. Science, and the fact that they deny that they are "friends".
When he is helping her buying a computer, an old classmate of hers shows up and tells her that he isn't surprised that she hasn't changed at all, and that she was still very "weird". This makes Reiko self-conscious about it, as they were previously talking about how she could improve many things about herself. When she tells Switch about it, he replies that she was "okay" and that if she was just a normal girl, he wouldn't be more weird than she is, apparently. He lends his hand to get a revenge on that guy, while giving Reiko a make-over that made her feel beautiful even if it was for one time only.
Switch helps her again with the whole Fortune Teller incident, as he explains to Bossun and Himeko that he wouldn't like to see her influenced by the Fortune Teller, because "she wouldn't be herself".
There was that time Reiko wanted to do a film for a horror film contest, and she wanted the help of the Sket Dan to shoot it. Switch reclutantly says that he wouldn't do it, although Bossun and Himeko gladly helps her, but at the end he gives up and takes the seat of the director. It's up to you to think if he does it for her sake, or if he is fed up with the whole situation and wanted to do a better film to spite on their "awful" attempt of horror.
Just after Momoka clears up the Onihime's impostor incident, she helps the Sket Dan to do a show for the kindergarteners (as part of a challenge/punishment from the Student Council, since she and her friends weren't supposed to be on Kaimei's school grounds after-hours, as she wasn't a student from there). They finally decide to do a puppets show based on her experience with them, and she has the role of the narrator. As long as the narration goes, she can't hide her feelings about the story's parallels to her own, when she met Himeko and the Sket Dan, as it helped her realize that she was glad that she met them, since she also needed new friends.
During the Kaimei Rock Festival, the Sket Dan (as The Sketchbook) does a cover of The Pillows's "Funny Bunny" dedicated to a new friend of Bossun who is a violinist, as she was close to give up her dreams of being a professional musician. It motivates her enough to keep studying music abroad.
The finale of "Ogress" offers a few moments regarding Himeko's past and present:
When Himeko reveals that she is Onihime, neither Captain nor Bossun want to distance themselves from her, and they accept her for the person that she is. Bossun even tells her that he needs "her" to form part of his idea of a club helping other people.
Himeko gives a narrative speech about how her hero, who used to be her favorite TV character, appeared before her ("dripping with sweat") and rescued her, despite the fact that she was a delinquent. She ends up crying on Bossun's shoulders.
In the present, Himeko reconciles with Arisa after she apologizes for all the problems she caused her.
Bossun, who always struggled knowing that he was adopted and that his blood relatives were deceased, finds out that Tsubaki is his twin brother in "Happy Rebirthday". They manage to calm down their rivalry differences and accept that they are siblings, while also accepting that their relationship isn't going to change from one day to another. They wish to each other a happy birthday afterwards. But the touching moment happens later when he walks alone after the closure of the Culture Festival, and realizes that he isn't alone anymore.
The farewell rally plan that the Student Council organized to Agata (with Bossun's help), as he was leaving his President position. The anime even goes further offering a song performed by the Student Council's voice actors as the ED theme of that episode.
During "Christmas Card", the Sket Dan has to deal with Morino, a friend of Fumi Segawa, who is a hikkikomori that decided to stop going to school because he felt that his art was worthless. Knowing that their own Switch was one too one year ago before the events of this chapter (and that he was also difficult to drag out from his house), Bossun and Himeko decide to help him, too. With the experience beforehand, they know that Morino isn't going to be easy to help, since it's up to the person to decide if they still want to be a shut-in or not. They, then, decide to show their feelings, that "he isn't alone", and that "they are his allies". There doesn't seem to be a way to do so, unless they apply something that would motivate him to get out from his house: doing a Christmas Card. It's emotional in a way, because it's not only the Sket Dan who do it, but their friends as well. And guess what? At the end, it ends up motivating him to get out from his house and keep doing his art.
Tsubaki gives some final words to the 3rd year graduates (Agata and Shinba's generation), and he ends up crying in the middle of his speech because it is more dedicated to Agata. He, however, stands up and tells Tsubaki to stop being too serious about the speech (since he is doing so as the President of the Student Council) and that he can say whatever he wants to tell him.
When it is his turn, Agata gives his (improvised) Valedictorian speech as a reply to his juniors.
"(...) I have only one thing to say. Regret nothing. Take responsibility for the way you spent your time! Only fools regret! When you're just having fun, you could get to know more friends! 10 years down the road, your experience at your part-time job could come in handy! How you spend your three years here is always your choice! I'll kick your ass if you complain about how boring your school life was! Never look back! Look forward! Move forward! Move forward! Move forward and don't look back!
Switch's first time talking to Bossun and Himeko in chapter 286. Dear lord... And the Group Hug after that with them (including Switch!!) laughing while tearing up is just... Oh my...