Rider
Rider let out a small chuckle at Rin's response to Sakura's assertion, before Rin answered the question she had asked in Sakura's stead. Considering it to be an acceptable suggestion, and seeing no objection coming from her master, Rider did as Rin had suggested, picking Sakura up before allowing Rin to climb onto her back. Moving quickly but carefully, Rider quickly got them back home and they entered the house. Rider could sense Sakura's excitement as she ran to the living room where she would, presumably, find Shirou, and followed after her with equal excitement, curious to see what she had in store. Sakura, however, had other ideas, asking Rider to wait outside. At first, Rider felt a little disappointed, but Sakura had asked her to remain in earshot, so she clearly did want her to hear what was going on. Most likely, she just wanted to give Shirou some privacy.
Hmm, I wonder what she has. Some sort of outfit for him, maybe? Rider thought, uncertain about the need for privacy.
Standing just outside the room and listening in intently and with excitement and anticipation. Rider could hear Shirou pipe up almost as soon as Sakura entered, greeting her cheerfully and asking about her day. However, Rider could tell from the sounds of Sakura's footsteps that she was walking towards him and, as she drew closer, he spoke up once more, his voice full of confusion as he tried to ask her what she was doing. Rider frowned, wondering what was going on until, suddenly, Sakura dropped a bombshell.
"Senpai, marry me", she asked with far less emotion than Rider would have expected.
Wait, did she? Rider thought, momentarily confused.
Then, she connected the dots.
Oh, of course..., she thought as she remembered what Rin had said, and the protective way Sakura was acting towards her bag.
She must have got a ring in the shop. That's what Rin meant by "give it to him so he can give it back to her".
A bright smile came across Rider's face as she came to recognise what Sakura had wanted, and what it meant. She and Shirou were going to get married.
After so long apart, that must seem like a dream come true to her, thought Rider with a smile.
However, almost as soon as the smile had formed, it disappeared as she heard Shirou's shocked response.
"Sakura are you serious? You shouldn't make jokes about stuff like this", he said.
An angry and confused look came over Rider's face on hearing his response.
Is that a no? Surely Shirou would never do that to her..., Rider thought as Sakura began to tear up.
Rider breathed deeply, holding back her desire to eviserate Shirou instantly for making Sakura cry like that, hoping that it was, in fact, just a misunderstanding. And, sure enough, Shirou soon grabbed Sakura into a hug, and gave her a firm response.
"Stop. I didn't mean it like that", he said. "Of course I'll marry you. We'd been talking about it before you disappeared, right? Why wouldn't I want to?"
Rider breathed a sigh of relief on hearing his response, before breaking out into another bright smile. She noticed the nervousness and uncertainty in Sakura's next question, but she knew everything would be OK and, sure enough, Shirou reacted positively, confirming the arrangement as the two of them continued to hug.
Uncertain what to do and wanting to go in to congratulate the happy couple, Rider sent a message to her master.
Should I come in now? she asked, not even attempting to hide her excitement and happiness at this new turn of events.