As an alternative to Kunai, these Tenno throwing stars do less damage but they come with expanded ammo capacity and a higher rate of fire.
The Hikou is a throwing weapon for the secondary slot, released in Update 9. It has a lower base damage than the Kunai and Despair, but a higher fire rate and base magazine size. Like its counterparts, it can also be hard to aim with because of its arrow-like arc projection.
The Hikou can ricochet (rarely) off surfaces, as floors and walls. Ricocheted shots can damage and kill whomever gets in the way.
The Hikou are quite similar to the Kunai, the main difference being about half the damage for twice the fire rate. Regarding this, Hikou are slightly superior, dealing 5 more damage per two thrown, which would equal 1 Kunai in terms for rate of fire. In other words, the Hikou trades a slight DPS upgrade for ammo economy when compared to the Kunai.
The Hikou are based off the Japanese throwing stars from ninjutsu tradition. Throwing stars were primarily used as distractions, and were often called the "invisible blades" due to a thrown star being able to cut enemies unseen from any direction.