> Why was he dangerous and disturbed?
>You do not fully understand what he did, or how he did it exactly, but he was at the center of an incident wherein every coin in Gensokyo was taken, and replaced with a gem. As you understood it, these gems were not proper minerals, but converted from his extensive literature collection (Patchouli made some passing reference to pearls of wisdom, which explained nothing). From what you've gathered, he intended to take this seized fortune; or seized economy as he called it, and barter it with the powers that be to shift the nature of the universe into something where anything could be bought or sold, aspects of the self, seasons, in theory anything.
>As you understand it, he was something like a priest, devoted absolutely to the concept of exchanges and the inherent inequalities of such. Somehow, he managed to derive a kind of faith from that, and a kind of power, gathering it under everyone's noses while posing as a simple eccentric. Then he unleashed it all at once. Since being stopped, the Myouren Temple has been trying to treat him, with some success.
>_