Handlers and Guides
A handler, rider, trainer, or guide, these all terms refer to the same thing: The one taking care of your Kukuri. The most common term is a handler.
Now, handlers are the most free things about the group. The only art requirements are that your handler is shaded (visibly) and is bigger than 150x150 px. Otherwise they'll not be passed as handlers nor will you get the handler FP bonus from it.
This doesn't have much lore-centric reason, as Kukus can be trained to be docile and thus handled even in smaller sizes, but anything smaller than that would be hard to see in the images, and thus some thing requiring a handler may be impossible.
There's two types accepted; a handler or a Guide. A handler must be sentient being, with hands and somewhat upright posture. They need to have thumbs, but both hands and thumbs can be created through magic or be mechanical. They are eligible for the FP bonus and can be used in traveling activity.
A Guide can be a sentient animal or another ARPG creature, as long as they're sentient enough to handle a kukuri. The presence of them allows for traveling activity to be rolled and can replace the wild kukuri or parent in wild training. However, they're not eligible for the handler FP bonus.
Your handler can be other closed species, your own species, or anything you desire as long as they follow the rules given above. They can even be shapeshifters!
One Kuku can technically have as many handlers you wish them to have!
When handler is required in activity/training/etc., it does not have to be the handler listed in your Kukuri's import to count as a handler. Any character that qualifies as a handler is counted as a handler.
In activities, handlers, guides, and starters can be freely interchanged.