Assuming SE intended for Kaeshi: Higanbana to be used in 2 target situations, then an idea I'd throw in for it would be this. Make Kaeshi: Higanbana deal more initial potency(the initial hit not the DoT). Then when Kaeshi: Higanbana goes off, whichever other target was hit with the normal Higanbana also takes that same amount of initial damage. Just enough damage that it's worth more than doing normal Higanbana twice and opting for Kaeshi: Setsugekka instead.