I can't believe I'm doing this... 

Hi there! I have had this idea for a little while now, and I guess I started getting curious about whether or not this was a story idea that people would actually find interesting in any way. I have no clue exactly what will happen now that it's out there, and it's definitely not finished concept-wise, but we'll see where this goes, eh? 

Here's what I have: 

In a fairytale-esque world, there is a legend of a town in which many nekomimi (cat-persons, essentially) live. In this town, collars are a very important symbol to the nekomimi, as they hold a certain significance pertaining to their relationships. 

There are now humans living in this town as well. For some mysterious reason, upon entering, a magical jewel is generated for each human that enters the town. This jewel can come in a multitude of shapes and colors, and the size may vary slightly, though all of them are still fairly small (only a few centimeters in any direction - this is very important due to their function). When given to a nekomimi, this strange item can awaken inner powers and allow them to use magic. Using this, a human and a neko may become a powerful duo and maybe make even miracles happen, but beware! These jewels hold a powerful secret, one that can easily save or destroy a human life: 
These jewels are the manifestation of a human's heart. 
All of the emotions a human may feel connect to the power in these precious stones, and similarly, all the love a human feels becomes the magic energy that both protects the nekomimi in possession of it and gives them the option of protecting the human from whom the jewel was received from. The downside to this is that, should anything happen to that jewel, the crystallized heart of that human, the consequences will be devastating. 
People don't necessarily die, but around 92% of the time, they do. Those who are lucky enough to survive would probably be better off dead, as either their ability to feel has been completely destroyed, leaving them as good as zombies, or they can only feel immense pain for their rest of their lives, which normally does not continue for long since their agony often drives them to find some way to end them. So, take care when giving away your heart, as a false love will cause only one's own painful demise. 
The nekomimi have traditionally placed a great value on these jewels, as they symbolize the ultimate form of trust for humans, and those who accept the hearts are tied to the owners forever. Or at least until something happens to the jewels that carry them. To keep the jewels safe, it is common in their culture to have a collar crafted to hold them, and those who come to the town are highly encouraged to see the Heartcrafter to have them set into a collar. When a human and a neko decide to bond romantically, the human gives the collar to the neko, who proudly wears it as a symbol of trust and belonging. (It is a proposal of sorts, but the culture does not necessarily require a couple to get married after the gifting of the collar. That being said, it is not often encouraged to gift someone with a collar as a mere confession, since all kinds of things can go wrong, but nobody seriously cares enough about when you give your collar away. It's about equivalent to the world's most potentially dangerous pinky promise, that's all. Also, the neko does have the option of returning the collar if the relationship does not work out, but again, you don't want to give it to a neko if you can't see the relationship going anywhere, as the collar cannot be forcibly removed. The neko pretty much has complete control over what happens to your heart.) 

So, will you take a chance and entrust your heart to someone? 

[hider=More about these hearts] 
1. The magical properties of the jewels are caused by human emotion, love for the possessor being the one that allows the neko to actively use magic. 
2. The abilities a neko may unlock with these jewels are only a few in number, although there are both passive and active magics that may be unlocked. 
3. After a certain amount of time with the jewels - this is different for each couple depending on the person and when the collar was gifted - the neko develops a certain sense specifically for the human they received the jewel from. This sense allows the neko to be able to tell when the human is in danger, as well as a few other things I will determine later, but is by no means a way to use active telepathy. It may allow a human and a neko to act more in sync, however. 
4. Collars must be removed to destroy hearts. This means that all characters in danger of having their hearts destroyed do have a chance to take back the collar before an untimely demise. I can't have people dying all over the place. (This will be posted in the official rules, too.) 
5. Magic can only be used by nekomimi while they are wearing the collar. They may use any physical abilities without it, but magic only happens when a bond is struck. 
6. The magicks that can be used through the hearts depend on the human. The strength of the magic and ability a neko has with it depends on the mutual love between the two. So yes, a neko will have trouble using magic if the feelings toward the human falter, fade, or simply do not exist. Also, if a human gives a heart to a neko without feeling any love toward them, not only is that a very stupid idea, but no magic will be activated. 
7. Collar magic is not limited to attack magicks, but only a certain number of magicks may be used, and they must be determined by the human. I suggest you come up with a strategy for the magics you come up with. Also, if a human manages to switch lovers, they may exchange one magical ability for another to match their new relationship. Should a human return to a previous lover, however, they are stuck with the previous magicks they used with them before. 
8. Collars can neither be forced on or off anyone.[/hider] 

[hider=A bit more about the collar culture] 
Traditionally, a nekomimi is in charge of defending the couple and/or eventual family while the human is in charge of providing for them. This is not exactly necessary for a relationship, though, as the two may switch off between roles whenever they feel it is practical for them. This only really became a tradition in the past because of the defensive abilities a "claimed" nekomimi develops from using the collar. A human may defend nekomimi, though they may not be able to use magic. Likewise, a neko is considered perfectly capable of providing for or assisting in the providing for a partner and/or family. They may even be able to use their magic to help out with this.[/hider] 

[hider=Other Pairings] Nekomimi may form relationships with other nekomimi, as that was actually what they did before humans became available as partners in the town. Since the nekomimi do not form crystallized hearts upon entering the town, their relationship customs tend to be different. (More on this later, as I have decided nothing about it.) 

There may be other races introduced eventually, but this was all I had for my original idea, so I would have to come up with completely different customs for them. I doubt collars would work for all races, anyway. Maybe Inumimi, and at a stretch, usagimimi... [/hider]

Also, nekomimi do not traditionally use weapons. That would be a humans-only thing. Don't get upset, they still have all their cat-like features, including claws and teeth. AND they have MAGIC. I'm still worried about them being overpowered, though I hope that allowing the humans to choose their magic fixes that enough...

So, yeah, I guess we have a bit of a romance RP idea here. It probably needs work, but I'm open to suggestions. 
Also, this would be the first roleplay I would ever start, so I would probably need a couple of co-GMs to help out, preferably at least one who has some experience as a GM.