Remember this? I think this line also brings it up fairly well. Bringing salvation to someone (as the one Shirou received from Kiritsugu) isnāt the same as save everyone/become ally of justice, the ideals he pursues. In Unlimited Blade Works, Shirou isnāt pursuing happiness or salvation, but the satisfaction to see this ideal fulfilled as part of his childhood dream (Heavenās Feel, will be the opposite choice). Now with that aside, letās take a look to what the heroines think of those ideals and how they impact in general of the role.
Sakura and Rin, as their routes, play as contrast. Rin is critical of the ideal and the path Shirou leads there; she knows how it ends and she knows it sucks and actually thinks Archerās right in complaining and regret. Her route is, ironically, the one Shirou embraces ideals over salvation, itās someone like her who doesnāt buy on his ideal, even if she sometimes acts to humor and support it, what may keep him from getting a complete bad end. We donāt know what kind of end thatāll be. The ending is ambiguous in everything but the certainty Shirou will follow his path.
On the other hand, we have Sakura, a girl who adores and admires his ideals, who would have played his eager sidekick if she had a chance. She considers that lifestyle Shirou leads, unlike Rin, admirable and beautiful and would never want to change it (now Rin sees Shirou as admirable too but she doesnāt want him to end up that way and she wishes he would think on himself in UBW). Rin cries because he confirms his resolve to her after Illyaās death, Sakura cries because Shirou tosses his ideals of being an ally of justice to choose to bring salvation to someone: Sakura herself. She has a conflict of interest, overjoyed as she is, she mourns and even tries suicidal actions over grieving this sacrifice Shirou makes for her. Shirou who has chosen not thisĀ ājusticeā of saving everyone but the happiness of protecting the smile of his loved ones will need someone like Sakura who, because he probably lost the memories of Saber and Kiritsugu (we do see the moonlight memory shatter, didnāt we?) will remind him of that inspiring ideal in the bliss of mundane and domestic happiness they achieved. Because Sakura admired that ideal and loved it.
Rin and Sakura didnāt get exactly what they wanted in the beginning, but they were what Shirou would need in the way the route played (Note this isnāt white/black, there are times Rin encourages Shirouās heroism while Sakura prefers he stayed safe, but in general, I am analysing the big picture. Rin had a desperate breakdown because Shirou would cling to that path vs Sakura who had a breakdown for the opposite reason). I think they were happy in those endings, regardless.
What about Saber? Saber is the heroine who shares those ideals and lived them. If Sakura admires his path and Rin criticizes it, Saber understands the pains and the fruits of that path (she could have been easily a mentor figure, but not in this format). She wanted to protect everyone and preserve the smiling faces but it never happened and, like Archer, she regretted the bleak hill that awaited for her. If Sakura and Rin are to provide a support with their presence, Saber is there to set an example,Ā like Kiritsugu, in this aspect. She cannot stay because, like he has his path, hers is just as important, their fates intercepted briefly and then they separated again. Shirou in Fate doesnāt need to choose salvation for one or save everyone, he accomplishes both by bonding with Saber, theĀ āking of idealsā and the girl who was drowning in regrets. He gave her salvation, and thus gave himself salvation, and he went on the path she also proudly marched on, looking at the stars. Their reunion happens once they finish their duties. Because thatās what Shirou needed there. He didnāt need Saber to stay (he wanted to, tho). He needed her example and the hope one day he would reach that shining star. Saber had her own ideals too, she gave her Master what he needed and obtained peace of mind to finish what she started, harboring the hope of meeting again after a long wait.
Each heroine plays a role that befit the storytelling of the route, the execution could downright awful sometimes, but it works with each of their peculiarities and itās up to us to decide what we prefer as outcome. But I wanted to address something that is almost always overlooked: the heroine relationship not with Shirou as person but with his ideals and the way they can perceive the path he will lead; and what this could mean in the outcome of their routes.