Rich and glamorous, they were both unmistakable standouts in Japan’s staid business circles with their brash talk of smart investments and fearless criticism of the status quo.

But within months of each other, Yoshiaki Murakami, 46, a bureaucrat-turned-fund manager, and Takafumi Horie, 33, founder of Internet services company Livedoor Co., had fallen from grace — arrested by Tokyo prosecutors on charges of violating securities exchange regulations.