Cute art and I like the concept! It's very short and I don't mind that, but if the level is going to be that short the player shouldn't be crazy fast. She controls kind of like sonic, and if that's how you want her to control then a longer level designed with a faster character in mind is needed. Or just slow her down!
I think more could've been done to sell the 'shrunken character' aspect of the game. The level kind of just looks like any other, and I would have no idea Renko was supposed to be smaller if not for the story text. Why not have blades of grass as tall as she is or giant flowers? Anything would work as long as it's a big version of a small thing.
For your first time using Unity this is pretty good! The game ran smooth and I personally didn't encounter any bugs. Would love to see this expanded on!