Hiramekarei features a wide, flat blade with two curved indentations near its base, creating a sort of cross-guard. Two handles are connected to one another by a short length of cord, earning it the title of "twinsword" (双刀, sōtō). The overall sword looks like a flounder fish in shape. When not in use, Hiramekarei is wrapped in bandages.
Hiramekarei is capable of storing chakra. With the command "Hiramekarei Unleashing" (ヒラメカレイ解放, Hiramekarei Kaihō, Viz: Hiramekarei Release), the stored chakra is emitted from the holes at the tip of the blade. The chakra rapidly coats the sword and can be shaped into various weapons, such as a hammer or a long-sword. The more chakra that is stored in Hiramekarei, the larger the size of the manifested weapon. This discharge of chakra causes the bandages it is typically wrapped with to unravel.
It can also create a large amount of light blue, fish bone-like crystals that can inflict great damage and restrain the target's movements. Hiramekarei can also split into two swords, each with a single handle, and in the anime, the feature allows for two different individuals wielding it at once.
- This is the only one of the seven swords not to have a direct kanji translation, due to its name being written in katakana.
- Both hirame and karei are Japanese names for species of flounder. The flounders with their eyes on the left side of their body are called hirame (鮃, 平目, 比目魚), while those with their eyes on the right side are called karei (鰈). Befitting its name, Hiramekarei is shaped like these fish.
- When the previous generation of the Seven Swordsmen are reincarnated, only Mangetsu Hōzuki and Fuguki Suikazan do not have their swords as both Hiramekarei and Samehada now have modern owners. Because Fuguki is known to have been the wielder of Samehada, it is presumed that Mangetsu was the wielder of Hiramekarei.
- In the anime, Boruto Uzumaki briefly wielded one half of Hiramekarei.