Everyone Steven meets is a friend, and he always tries to help his friends.
The story begins when Steven decides to try out this “school” thing he keeps hearing about from Connie, and once Pearl discovers that the point of it is just learning, she produces a magic mirror…but is disappointed to discover that the mirror won’t respond to her commands.
Pearl: It is in pretty rough shape. It must finally be broken.
Steven: It doesn’t seem broken to me.
So he runs around town with the mirror until he discovers that there’s some magic left in it, after all, as it warns him when a car’s about to run into him.
Steven: What just happened? You work! This is so cool! What’s it like being a mirror?
Mirror: “You work!”
Steven: So you can repeat stuff?
Naturally, the first thing he does with this powerful magical artifact is go use it to play a joke on the Mayor (who had just almost run him over).
Once he’s alone with the mirror, it starts to form more complex phrases using words that other people had said “in” the mirror.
Mirror: “Steven!” “is” “a new friend”.
Steven: You’re my friend, too!
It’s honestly kind of unsettling how the mirror combines words from different people with different emotional inflections to express a thought, but to be fair, it only seems to have a day’s worth of interactions to pull from.
But that’s still creepy, and it’s about this point when you seriously start to question the mirror’s motives, and in turn wonder how Steven doesn’t think it’s creepy, too…especially when it responds to Steven’s suggestion to show it off to the Crystal Gems with a resounding “No”, despite his reassurance.
Steven: I fixed the mirror!
Pearl: Excellent work, Steven!
Steven: You didn’t tell me it’s like a person.
This is their immediate reaction to that statement. I’m not sure if this is supposed to mean they have no idea what the “Mirror” is, or they do and just didn’t want Steven to find out, or a little bit of everything. Either way, they’re clearly shocked by this turn of events.
Pearl: It’s talking to him? It shouldn’t be able to do that, it should only be following orders…
All three of them are frightened of it, and Garnet tells Steven to give it back so they can keep an eye on it.
Garnet: Steven. Don’t make me have to take it from you.
Steven: It doesn’t want to go with you! Can’t you hear it screaming?
Garnet: Steven, it’s just a mirror, a tool. It can’t want anything.
Poor Steven is caught between his new “friend” and his family, a predicament he’s never faced before. And before he knows it, he’s hit Garnet in the face and run out the door.
Steven: I’m sorry!
Garnet: That little boy is in big trouble.
Well I guess Garnet can be kind of creepy, too…and you definitely don’t want to make her mad.
But now that he’s done it, Steven has a ton more questions for the mirror.
Steven: What am I gonna do? What’s their problem with you? Are you trying to say something?
Mirror: “Away from home”…”let” “me” “out!”
Then it indicates that he should remove the gem from the mirror (which also proves that it had more control of what it could show than it had let on).
In a less idealistic universe, a child trusting the magical artifact against the wisdom of his guardians could very well end in tragedy. But this is the Steven Universe, where trusting others, even one you’ve known for less than a day, is generally rewarded. (why yes, I do have Thoughts about this, but I’ll save them for another day)
It turns out to be another Gem like the others…
Lapis: Thank you. You didn’t- you actually talked to me. You helped me! It’s Steven, right? I’m Lapis, Lapis Lazuli. Are you really a Crystal Gem?
Lapis: But…you set me free.
Steven tries to stop the Crystal Gems from hurting Lapis, but it turns out he needn’t have bothered – she’s plenty capable of defending herself.
Lapis: You. You three knew I was in there, and you didn’t do anything! Did you even wonder who I used to be?
You can’t help but wonder how much they actually knew – on the one hand, you’d think they’d understand that “gem powered” means “powered by one of their own people”, but on the other hand I find it hard to believe that they would knowingly use someone like that.
Lapis: I’m Lapis Lazuli, and you can’t keep me trapped here anymore! They’re not gonna let us leave.
Lapis: Steven, come with me.
Steven: B-but, but I…
Lapis: Fine. Don’t trust them, Steven. Goodbye.
Then she walks off into the sea (as water is apparently her element), leaving a whole host of questions in her wake.
Steven: So that was another Gem?
Garnet: Steven, you’re grounded.
Fortunately, this is a two-parter…