The Hedgehog Yo-Yos, are Chikusa Kakimoto's weapon. They are butterfly-shaped yoyos, with long string for ranged attacks and small holes at the sides from where Chikusa is able to shoot many needles towards his opponent. Chikusa seems to able to perfectly control their direction and he is able to fight with two yoyos at a time - one in each hand. Not only the yoyos, but also the strings seem to be harmful, as he was able to slice Gokudera's dynamites with them. Moreover, the speed the yoyos move towards or even change direction is extremely high. The needles inside of the yoyos are millions, until a point where Chikusa has a needle "shower" move that's why they are called "Hedgehog Yo-Yos."
The yoyos are red, with the butterfly style, and have a K at the side, probably for "Kakipi" which is his nickname.