[i]"That may be so, but --- Is it really not good for a sorcerer to be exposed to others?"

"Indeed, it's bad. Although it wouldn't really matter socially, the power of your sorcery falls. Do you know the origin of the word 'mystery', Kokutou?"

Touko-san asked that as she brought her body forward on the desk.

"When you say mystery, do you mean the sort of mystery in mystery novels?"

"In a way. Not the detective novel sort, but mystery in the mystical sense."

"Yeah, I do. It's originally Greek, not English."

"... Well, that's true. In Greek it means to close something. Signifying stagnation, concealment, and self-completion. You see, a mystery has meaning in the fact that it is a mystery. Keeping it hidden is a nature of the technique. A sorcery that has had its nature revealed can't become a mystery, no matter what kind of supernatural methods it uses. 
It's nothing more than another method. Once that happens, that sorcery instantly becomes weaker.
Sorcery was originally magic too. In short, there was no question that the strength was pulled out from the origin that was its source. Should we imagine for a moment that there was something along the lines of a 'mystery that makes you rich'? Let's say that this has a strength of 10. If only one person knows it, they can use the entire force of 10 of its power. But if two people know it, that it gets halved into two units of 5 and gets used like that. See, it's gotten weaker, hasn't it? The way of expressing it may be different, but I think that this is a fundamental rule in regards to everything in this universe."

I can't understand all of what Touko-san is saying, but I think I get the point she is trying to convey.

If concealment and obscurement is the law of existence that thing called sorcery exists by, I understand why mages would be reluctant to reveal their sorcery in front of others.

"In that case, you must do as you please where others can't see you, Touko-san."

"Nope, I don't."

Zkk, Touko-san started talking as she stubbed out the cigarette in her ashtray.

"I wouldn't have a choice in a battle between mages, but otherwise I don't use it even if I'm alone. The only time I use sorcerous techniques is when it's required for a ritual, or in a ceremony in order to proceed to the next level."

Some time around the medieval era or so, an organization called the Association was formed. Because of their excessive regulation of sorcery, the Association foresaw the degeneration of mages. So they took the power of their organization and turned sorcery itself into something that is never revealed. What they did was to take a mystery that was visible and turn it into a mystery that no one knew about. As a result, mystery began to disappear from society.[/i]