Rider listened with a mixture of extreme concern and confusion as Sakura explained her lack of prana to Rider in a very laboured manner, before collapsing onto Rider's back, holding tightly onto her top. In particular, she was very confused by the mention of her circuits not being able to handle it.
I've never had that problem with my Sakura, her circuits have always been able to supply prana faster than I could possibly use it, and Pegasus isn't all that prana-intensive to summon. Maybe magic in her world works slightly differently. I'll have to take that into account in the future.
Still, Rider felt rather guilty. She had used quite a lot of prana in the last 30 minutes or so, and Sakura was now supporting two servants rather than one. Plus, Caster had not exactly been holding back either. So, it wasn't really surprising that Sakura was feeling the effects somewhat, even if the part about her circuits not being able to cope was rather unexpected.
Before she could apologise, though, Caster spoke up, his tone much more hostile and condescending.
“Rider, please refrain from overusing your powers. Sakura is maintaining two servants now, for better or for worse. Please think about this in the future", he said.
Rider couldn't believe his attitude. She'd just saved them from being shot at by magical beams that would almost certainly have instantly killed Sakura had they hit, and he was complaining about her doing so.
"I am sorry, Sakura. I did not mean to make you suffer like this", Rider said, the sadness, guilt and concern clear in her voice. "In the future, I will keep this in mind when I consider when to use my abilities."
Then, she turned to Caster.
"Caster, what else would you have had me do? Leave us there to get shot at?", she said, angrily.
"I hate seeing Sakura suffer like this, but I would rather this than her having a hole like the one through Pegasus' wing in her chest", she continued, more softly, her concern for Sakura and guilt clear in the way she spoke.
Then, Rider lifted one arm behind her and over Sakura's head, rotated the top half of her body around so that she was facing towards Sakura and gently placed her arms around her master, still remaining seated on Pegasus with her legs facing the opposite direction from her arms and head.
"Sakura, I'm going to have to de-summon Pegasus now. He can't fly like this, and I can't control him easily in this state.
Caster, can you lead the way back home? I'll carry Sakura", she added, awaiting Sakura's confirmation to dismount and then de-summon her mount.