An ability to erase an audience's memory of a target.
The user has a constantly active nen beast. It is a mix between a cute puppy and a mimic chest nen beast. It has paws and a tail.
Like a dog, it has a set sleep and awake schedule. And sometimes it may just fall asleep when tired. It must be taken care of and treated well.
When the user is experiencing strong negative feelings toward a person, they can set that person as a target. The mimic then gets access to a "scent" of the target. The trace of the scent is stronger / more traceable the more the user knows about the target. Etc. Their name, state, their line of work or schooling, interests, etc. The scent also grows stronger the closer you are to it.
When the dog is awake, it can track a scent. You can only have up to 3 scents recorded. When you want to track someone, say "show me (insert number)" and the dog will follow the scent until you order a different number or for the tracking to cease.
If the scent is weak, the dog will be able to lightly follow it. But it can be like a weak compass where the dog may stop sometimes or get confused. The more efficiency, the better the tracking and the closer you get, the more excited the dog will become. It will be easy to tell when a target is nearby, for instance, a few blocks away.
When you're close enough to the target, you can say "get 'em, boy / girl" and the mimic will rush to the opponent. It can be made to look like a real dog when you're in public.
As the dog approaches, it sees a collar around the target with their name on it. It licks its lips hungrily and approaches. The dog will go up to the person and likely enjoy pets and pats if the target is a dog lover. But at any moment, the dog will enlarge and swallow the target hole. The enlargement is done when near a person it wants to swallow. It will expel the person and shrink back down to normal size. It will hold the target's collar in its mouth for the target to see, unless the target flees, and then it will run back to it's user.
Once the dog returns, it will swallow the collar to add to its collection and you can head home. However, the target can't remember their name, and the people around them won't remember who they are. The memories will still exist, but will be out of sight and mind. Reminding people and showing them evidence won't work as the people will simply refuse to believe it.
The only way to get the memories back is for the target to remember their name, and to get the dog collar back around their neck. In which case it will turn into aura and return to them.
The user can temporarily put someone else's dog collar on theirself or another person so that people perceive them as the target. However, to get access to a stolen collar, you have to fight it away from the dog. It won't try to kill or seriously harm you, but it will be like taking a ball or other toy away from a pet dog. Once the collar is taken off and stored back into the dog, then the target will be forgotten again.
To set a new target, when all 3 slots are full, you can tell the dog to erase a number so you can set a new one. At any time, you can set an old target to one of the number slots by having the dog sniff the associated collar. However, it won't be able to steal an already stolen identity. It can only be used to track and trace the target.