Serie refused to teach magic for the King as Flamme requested because she wanted magic to be special. Then she created her own Continental Magic Association beyond the national levels, placing herself above the King. Here she can keep both Flamme's request to teach magic and her own principles of magic only for the worthy.

It seems, flashback from this episode between Frieren and Serle a little bit sheds light on Serie's character. A walk we saw her memory of the small Flamme was all over the place. May be she saw her as child not only when she was child, but when she become adult too, like Frieren still see Fern as child as we know. A little possible hint, that sentence "but humans cannot afford to delay" in original Japanese, if I understood it correct, was "but those children cannot afford to delay". Serie's reactions to Flamme's death show her true emotions, despite her attempt to conceal them. She spoke of Flamme's achievements proudly, like a proud parent talking about their kid, even though she claimed to have trained her on a whim. Serie's struggle with Flamme's death is evident, though she didn't want to admit it. The walk with Frieren was her way of coping, reminiscing about Flamme while expressing her grief, those occasional signs of sadness in her eyes. Ultimately, It seems Flamme understood Serie deeply, much like Himmel did understood Frieren. Despite tearing up Flamme's will, Serie honored her disciple's wishes in the end. From the way Series would react upon reading her will to the presence where Serie eventually took over for Flamme's request and found the continental magic association 50 years ago, in current timeline. It seems Serie is ok with mankind learning magic now, however she still believe only special ones deserve to learn the deepest or most unknown part of magic. So organization built by her are teaching magic for everyone, but only first class mages are allowed to request to learn special spells from Serie and are allowed to be by her side, to consume knowledge directly from her. It seems her mindset was a little bit changed by Flamme, and it is huge, because as we can guess Serle is ancient being even for Frieren. Another interesting detail at the episode, that Frieren taught Fern that basic offensive spells are enough to defeat modern mages, but when faced against herself, an opponent of similar strength, she uses far more destructive magic. It seems, she has to use spells that'll actually go for the kill. Sorry for long comment 😅 And thank you very much for reaction!

They are strong mages but I think if frieren wanted to go all out even all of them together will have trouble. Wonder how many spells she hasn't even shown

2:12 “So Fern, you thought about a way to kill Miss Frieren in the past?” Hehe, probably every time Frieren wouldn’t wake up on time. 😜

I don't think Serie is worried about humanity catching up to her or fears humanity's progress. I think Serie's more of a traditional mage compared to Flamme and Frieren, in that she only sees magic as a means to an end. Serie wants magic to be special in the sense that she wants to train the most talented mages and help them reach their full potential so they can advance magic and make it more powerful. She doesn't want to train average mages to help them become less mediocre, in her opinion. That doesn't advance the art of magic in her mind. Serie calls Flamme's favorite spell useless, because I think she values power or lethal potential of a spell. Flamme and Frieren see all spells as worthwhile regardless of power, because they all have a purpose, like making people smile or even a mundane use. It's like games will have players who only care about the meta and the best way to win the game, while casuals who want to have fun and will play the less effective strategies if it is more fun for them. What fascinated me about Serie is that accurately described humanity's progress and warned Frieren not to underestimate them, just because of their limited lifespan. That is interesting because at the start of this series Frieren originally didn't even want a student, because she thought their lifespans were so short that there no point to it. Earlier series Frieren seemed to almost completely dismiss humanity based on their shorter lifespans or overlook their accomplishments until Himmel died. That led her to this self-reflective quest. Now on her second journey with her second party Frieren is seeing the beauty of humanity and is seeing value in their shorter lifespans. Serie plays up that she only trained Flamme on a whim or said they never understood each other, in this flashback we saw how she remembered the times when Flamme was just a girl, her hopes and dreams, and even favorite spells. Serie already has the respect of humanity and appreciation for them that Frieren has only recently acquired. In the end as you both noted Serie did end up doing what Flamme asked of her.

The Idea that a human can catch up to an elf was seeded back with Qual in episode 3. Long lived species just don't care much about the passage of time and in the 80 years he was sealed humans had taken his spell broken it down and learned how to cast and defend against it making it nothing special. That inherently is also what Serie gets at that magic should be special but with what humans are capable of any complex spell can be figured out and replicated. Its almost like a hoarder in an MMO who wants to make sure no one else gets their unique mounts and items because they would no longer be just that; Unique. If we had to start from scratch with every person we would never get anywhere when it comes to progress but we build on what's come before us. Our limited time means we can progress far faster than a species that would rather bumble around in the woods for 100 years. Also always love hearing Killua's VA as Serie gives that HXH nostalgia...

Me 6 months ago: "Nothing matches the animation of Fate" Me now: "....well, you can't underestimate Frieren"