[stormy001_M1A2]

Spoiler:

in the game, Rin already liked Emiya from early days, she always observed him intently. One time she remembered most is when Emiya keep trying to jump over an obstacle despite being injured in the process. She was especially impressed by his sheer determination and spirit, thus have a thing for him.....Sakura was there too

Regarding about Rin and Shirou.