My guess would be Hikaru uses a scythe, they don't have info but looking at the pictures. They seem to be related to the undead and since they have a cat-like ghost, which I assume that's Kou. So I would think they are a necromancer, they can communicate with the dead as well as summoning ghosts and spirits with them. This is rather connected to the scythe than Hikaru themselves. Hikaru is more likely combine magic with the weapon, but opts more on melee range.
NP: you can either do Astaroth or the original, not evil version