I thought you should never use triangles? I was curious on looking to how does an anime topology look like. I've looked into pictures and videos and I thought the best way to learn took into it is to see it for myself. So I used ninja ripper to rip a model from Fate/EXTELLA (cause it's the only game in my machine for now). Her name is Tamamo:  Why does it have triangles here? I thought we should only use Quads?
Almost undoubtedly the mesh would have been modeled using quads since it is better to work with. However, any mesh is actually converted to triangles at the lowest level for rendering. By ripping the model out of the game you are picking up the mesh in a form that has already been optimised for maximum efficiency in the game - ie, already converted to tris so the game engine does not have to deal with the more complicated quad-based geometry.