Someone should be there to lean against her. It can't be him. Does that make him feel regret? He can't tell. There's no way to feel a gentle rain on the bottom of the ocean.

"Yeah, there are ways in the City to provide for us, like this building. Maybe that's why so few imPorts leave." He keeps looking at her so long as she's not quite fully looking at him. "Of course, I know you could handle it. Rin Tohsaka is the kind of person who decides she can do something, then sets her mind to a task and conquers it, even if others might whine about its difficulty."

He finally looks down, smiling in a detached fashion. "But I couldn't. You must be aware that getting used to a life like that would conflict with my goals. In fact, I fear that if I spent long enough here with you that I'd forget about my purpose in the Holy Grail War entirely."

It's safe to say this, he figures, because she doesn't know what his real purpose in the Holy Grail War is. She's allied with Shirou Emiya, shared her body with him, even hinted that he's still hers--so there's no way she'd consent to live at the side of the wiser and more broken Emiya if she knew his goals. Naturally she'll just assume he's talking about the Grail, like any other Servant would be.

"I'm a really unreliable Servant like that."