It's a very short Shoujo Ai story. It doesn't have a turning point or a backstory but still gives you a warm Shoujo Ai atmosphere.
We have 2 characters and nobody else. And those 2 characters don't have a unique character or something interesting about them.
Just like described in the synopsis, our main character, Eriko wonders if she has been used by her friend Shino.
And that's it, there are no other things happening after we learn if she's using her or not. Could've been longer and had other things about their relationship. But it's still worth it for that 4 minutes it takes to read.