>>5739618I believe after the twisted plot against timespace Renko was the first shrine maiden assigned by Yukari after the death of the already existing shrine maiden and therefore ancestor of Hakurei Reimu.
This happened after she followed Maribel later to Gensokyo when she was already Yukari for a long time.
Yuyuko was original the only human of already existing human village that had contact with Yukari aka Maribel when she was new to "Gensokyo".
So after a while Yukari and Yuyuko knew each longer than she knew Renko "back then" and became very close friends.
https://www.youtube.com/watch?v=3bS0Y2if3wUbtw I also think ZUN had in mind that Maribel is from German heritage and Renko from Japanese heritage, cus of generic anime tropes heh
