Rider
Rider sighed as Vanguard started to speak to her in an almost-patronising manner, seemingly trying to encourage her. Still, she knew he meant no harm, and she had no real issue with him. She was quite happy to fight alongside him for as long as he was Sakura's loyal servant.
She continued to watch as the sentient suit of armour paced around in circles, thinking, before he spoke up once more.
"Still, it would be unwise to leave Sakura's side at the moment", he said. "There is no reason to leave at once, and our master is clearly troubled at the moment. I think it would be best to support her from the sidelines at the moment. What if Sakura went into another outburst like earlier? We would not be able to ensure Emiya's safety then. This command seal certainly did not help back then. It is still unsafe."
Rider pondered his words. She didn't think another outburst from Sakura was a real danger. Whilst Rin had seemingly been genuinely frightened by what had happened, Rider was pretty sure that Sakura was not being aggressive towards her. After all, Sakura's shadow magic was not something that would easily cause harm to humans, at least not without an intentional effort. They were more useful for grabbing things. Most likely, the shadows were a magical attempt at a hug. And, even if Sakura could have perhaps harmed Rin, Rider could not see any conceivable circumstance where she might harm Shirou. She had a strong subconscious instinct against doing so, as had been proven several times during the Grail War.
Still, despite that, Vanguard had a point. Sakura was in a fragile state at the moment, and going out might make her feel worse. Particularly Rin, who Sakura was very, very frightened of losing once more, and who was likely to be a sitting duck if targetted by whatever had killed Faust. But, at the same time, it was not true that there was no urgency to this. Any clues about what had happened to Faust would rapidly disappear, if they did not go searching now, then they likely would never discover what had happened.
Rider's thoughts were interrupted by Rin, who looked at the two of them, frowning.
"Did I miss something that happened with the two of you?" she asked.
Rider nodded in denial.
"No, there's no problem between us", she said, matter-of-factly.
"Vanguard, I do not think Sakura poses any threat to Shirou. Or to Rin, for that matter. Her earlier outburst looked scary, but I believe it was harmless. I do not think she would have hurt Rin even if she had succeeded in grabbing her. And, she has an even bigger mental block on hurting Shirou. He will be quite safe. However, you are nevertheless correct that it would be better to remain here rather than seeking a fight whilst Sakura is so unstable. She needs emotional support right now, not us putting ourselves in danger. However, if we are to discover who killed Faust, we will have to go now. If we leave it until tomorrow, then it will be too late, the evidence will be gone. So, I am not sure what the best approach is."