why does giyuu have a punishment name in demon slayer

Tang Zhen transmigrated to an apocalyptic world, where humans struggled to survive in various buildings that they built because the ground was covered in lethal dangers that were invisible to the naked eye. Tang Zhen transmigrated along with his mutated cell phone that was packed with miraculous applications. There were all kinds of cities – some could fly in the sky, some could submerge into the ocean while some could become invisible – and shocking secrets were hidden within them. The power of Tang Zhen’s city was… He established a city and quickly leveled up his army with speeding tools. Then, he dominated this alternate world by seizing other cities. He sat at the very top. Beneath his feet was a vast floating city guarded by dragons and surrounded by angels. Countless cannons were also set up at various corners of the city. A million miles ahead, in the depths of the ocean, there was another city as large as a continent awaiting his conquest.