Kurogasa is the 9th chapter of the Rurouni Kenshin manga.
On a stormy night, a man wearing a black hat has killed a group of bodyguards, their corpses pilled on the floor of a luxurious manor. He uses a strange power to paralyze his target, an Ishin Shishi who is scared to death as he is mercilessly murdered.
During the day, back at the Kamiya Dōjō, Kenshin, Sano and Yahiko are eating Kaoru's cooking, which Sano calls "terrible". Kaoru, in anger, starts throwing various objects at Sano, who uses Kenshin as a shield while Yahiko keeps eating.
Kaoru's fit is interrupted by the police chief who, entering the dōjō, asks to speak to Kenshin. Asking for forgiveness for the sword-bearing police incident, Tokyo's police chief asks Kenshin to take down a murderer called Kurogasa (black hat).
Answering that demand, Kenshin and Sanosuke go with the police chief to the mansion of an Ishin Shishi targeted by Kurogasa, Tani Jūsanrō. They stay there along with other bodyguards, to protect Tani against his would-be assassin. Come midnight, Kurogasa bursts in through one of the manor's window, killing one of the numerous bodyguards present.