When Yurn's given her first big courier job, she's nervous about traveling outside of the city for the first time, especially when she's told she has to wade across a river infested with sirens. Thankfully Jaze, an experienced adventurer Yurn looks up to, has been there before and volunteers to go with her. She seems to know all about the area and the monsters that inhabit it, and assures her sirens are harmless.It isn't until they arrive at the river that Yurn learns what "harmless" means to her friend. And that sirens are hiding more beneath their scales than she'd thought. But what's most surprising is her own reaction to seeing all this.This story contains explicit futanari on female scenes.