Why Rael only want to be friend with Yunifer?, it's weird. Because if some friend avoid me, then I just go find the other. I think Ishid also want to be close with Yunifer since the academy too, but thought he's not good enough. So he didn't like Rael to keep on approching Yunifer.
Especially when Yunifer refer to the stronger water mage which implied that she thought she's inferior than Rael.