The Hedgehog Yo-Yos are Chikusa Kakimoto's weapons. 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 yo-yos at a time - one in each hand. Not only the yo-yos, but also the strings seem to be harmful, as he was able to slice Gokudera's dynamites with them. Moreover, the speed the yo-yos move towards or even change direction is extremely high. The needles inside of the yo-yos number in the millions until a point where Chikusa has a "Needle Shower" attack, from which the name "Hedgehog Yo-Yo" is taken. In the future, Chikusa is also able to cover the needles in Rain Dying Will Flames, probably to increase the damage.
The yo-yos are red with the butterfly style and have a K at the side, probably for "Kakimoto," which is his surname.