The main character was in a research group on Earth and could use magic before being transported to another world. He tried to hide his powers in the isekai world, but was revealed after someone attacked him (it's been a few years since I read it so I'm not sure). He came with other people and was mainly a black and white manga
This is very possible to be Isekai Mahou wa okureteru!
The main character, Suimei, is a magician from our world who uses mostly math in its formulas and magic circles unlike the new worlds magic that is based in the 4 main elements.
He gets attacked early on and needs to unleash his magic at the woman who summoned him, together with his two friends, one of them being the Hero.