In Flight/Heartwarming

Entirety of Shirou's treatment of Akitsu. He was on the run, didn't trust her race one bit and was going out of his way to avoid them. And then he met broken, almost naked Akitsu sitting lonely in the middle of the park. Old habits kicked in and without a second thought he took her in and accepted her as his Sekirei, something Akitsu thought would never happen. And it only gets better from here, every time they interact Shirou makes sure if Akitsu is alright and comfortable. He is even determined to confront Miya about No-Pets Rule because Akitsu wants a doggie.
- It gets taken Up to Eleven, it took a Tantric Ritual to get Shirou to finally wing her.
- Shirou's thoughts prior to that moment are a CMoH on their own:

Shirou: Even if it was only a chance, even if it was one in a million, even if my assumptions and guesswork were based off hazy incomplete evidence and possibly completely unrelated coincidences, it was still a chance. And Akitsu deserved that chance. She had tried, so damn hard it was enough to make me misty eyed, to live past her condition. She had done everything she could, more than probably any other Sekirei in the plan, to be the best Sekirei she could, to be the most loyal and worthy person she could. Despite her fear, despite the hardship that she had been through, despite the shame she no doubt felt, Akitsu had given her all to me. I hadn't known what my impulsive decision to accept her oath would mean to her, not when I had accepted it. Now that I did, it was my obligation, no my duty, to do everything I could to repay her loyalty.

Kusano's and Shiina's reunion.
In the Twenty Sixth Wing, Matsu and the rest of the Sekirei tell Shirou that he is not alone, and that they will help him even if it means fighting Magi. Even so, Shirou has a new dilemma, he realizes that his belief that has cultivated to what he became and what would eventually happen in his future (Dying Alone on a hill of swords) is the greatest fear of his own Sekirei.