Stanley

He was the one that teached Shiro magic in her second life when she was a kid.

was called by Koji to teach Aarim, Silvia and Yin during the time Shiro went back to see her parents.

Background
There wasn't much known about him only that he was hailed as one of the greatest mages to have existed. His specialty lies in the fact that he had mastered the use of analytic magic. It was a type of magic that not many use much less master.

The main principles of analytic magic was that it would analyse the opponents magic and turn it against them.

But that wasn't all, even if Stanley couldn't see the magic circle, his senses when it comes to mana were top notch. If one wanted to know about magic, he was the go to person.

If you studied his teachings diligently, he was a very nice teacher and one that would make sure to try his best to help you. On the other hand, if you dismiss his teachings or ignore what he says, he will just give up on teaching you all together.