The ability to sympathize with other people. Putting it simply, it’s giving one’s own physical strength to somebody else.
As Kohaku and Hisui are particularly talented sympaths, they don’t just give their own physical strength, but also strengthen and support the mental and physical strength of their target.
Also, because this is sympathy and not empathy, even if the target is injured there won’t be any feedback for the sympath.
The method of sympathizing varies depending on the practitioner. For some, it is possible to sympathize regardless of the target’s will, while for others some sort of ritual is necessary.
The ritual is a switch on the spiritual plane passed down within a family, to control heretical abilities. It is a mental block implanted in the subconscious that prevents the ability from activating unless certain conditions are met.
……In other words, Kohaku and Hisui’s family must have been a bunch of perverts, huh?
- ^ Sometimes also translated as “Sympathy” or “Synchronization Ability.” Note that while “Synchronization” may sound like a two-way ability, this is actually just a one-way ability, giving strength without any feedback from the target.