The whole idea behind Key's nature is that he's supposed to be... the "key to the problem". He's always the one coming up with ideas, arbitrary as they may be. They do work, more often than not, but whenever Key himself is the better solution, he'll say otherwise, pressing that his plans would better get the job done. No matter what, he will always hold the belief that his ideas are the ultimate solution, because... well, he sees himself as the key to the problem!

This way of thinking is what gives Key his "chaotic and energetic" nature. He is never one to put others down, and hanging around him isn't the hardest thing to do (for the most part). With his self-confidence, he's acts with ambition, never backing down once he's in motion. He's also got a sense of humor, though it gets lost in the shenanigans he calls "plans". While this mindset can be a good thing on its own, his ideas can involve using anything to do anything, making him reckless.

He's always confident that his ideas work and are the best way to handle whatever he's up against. The moment someone tries to tells him "it's a bad idea" or "we should do something different," he becomes stubborn and insistent, sometimes refusing to listen. This is especially obvious when he is the answer. To Key, the fun in solving a problem comes from the way you solve it—like a puzzle! He may not be the best at puzzles, but the point is: using his power to get something done just isn't fun or rewarding in his eyes.

Arguably, Key has a good philosophy when it comes to problems... but his plans still tend to be impractical and/or insensitive in some way. His confidence makes it tough for him to realize that. However, thanks to Peri and their friendship, he at least makes an effort to be thoughtful. Key cares a lot about her, and that alone makes him remember to be considerate of his own friends...

Well, he's learning to. It's not like he's entirely socially inept!

Key is a copper-orange cupronickel key. It's not specified what "alloy" of cupronickel he is; he just is one. Because of this, he shares very similar properties to those alloys. In general, though, he is much like many other everyday keys, despite the impracticality of his design from a mechanical standpoint.

Key has the ability to unlock anything he is pointed directly towards. This includes any lock, whether it be visibly external or internal. He can also unlock a lock if he can, somehow, fit into the keyhole as well, defying any mechanical properties the lock itself may have. However, Key cannot unlock anything that is intangible. He cannot unlock an online account, or somebody's heart, for example. Those remain outside the "scope" of his ability.