Koyin works on a farm below the Hateno Ancient Tech Lab in Hateno Village, tending to animals such as Highland Sheep and Hateno Cows with Dantz. When Link first meets her, she is angrily talking to herself and holding a stick in her hand.
Should Link decide to speak to her, she is immediately aggressive toward him. However, she eases up a bit to explain her situation. According to Koyin, a group of monsters have been abducting her flock. This unlocks the quest "The Sheep Rustlers".
Koyin goes on to explain how she had driven off the monsters at another time, but is not certain enough of her ability to handle them all at once in their own territory. If Link asks her about Hateno Beach, she will tell him where to go. Once Link tells her goodbye, Koyin sighs and apologizes for being defensive. Until the quest is completed, Koyin is too concerned about the herd to go to sleep. She will stay up throughout the entire night to watch after them. Even the rain is not enough to budge her from her spot.
Once the monsters are taken care of, Link can speak to her again. She notes that her flock is calmer and asks him if he was the one to exterminate the rustlers. Should Link admit to it, she will say that she thought he would be the one to do so. If he simply bids her farewell instead, she stomps her foot and refuses to let him leave the conversation without hearing her out. Koyin rewards Link with ten bottles of Fresh Milk, noting that it does not feel like enough. She is pleased that she will be able to sleep soundly and offers through a stammer to speak to Link whenever he likes.
Koyin often mentions how Link protected her livelihood, pointing out how the health of her animals has improved. While she retains her sour attitude, she is a bit more at ease. When it rains, Koyin comments on how the soil smells like life itself.
Strangely, although she mentions sleeping soundly now that her herd is safe, Kyoin still does not go to bed at any time.
- "Koyin" — N/A (Breath of the Wild)
- "They'll pay! They'll all pay!" — Koyin (Breath of the Wild)
- "Hey, you. [Yes?] What do YOU want?" — Koyin (Breath of the Wild)
- "[Good-bye.] Cut it out, creep!" — Koyin (Breath of the Wild)
- "Oh, don't act so clueless. Although... Fine. You seem harmless enough." — Koyin (Breath of the Wild)
- "Forgive me, I've just been on edge with all these monsters running around. They come up from Hateno Beach to steal my sheep. If someone doesn’t do something soon, I won’t have any left!" — Koyin (Breath of the Wild)
- "I hate that gang of monsters on Hateno Beach… [Which monsters?] The stupid ones who attack anything that moves. Last time they showed up, I gave them a taste of my pitchfork. But I had second thoughts about following them back to their camp on Hateno Beach. I was mad enough to spit, but maybe not mad enough to take on seven monsters at once." — Koyin (Breath of the Wild)
- "[Hateno Beach?] It’s southeast of the village. Follow the winding road, and you’ll be there before you know it. It’s well-known enough that you can probably find it on a map, come to that." — Koyin (Breath of the Wild)
- "[Good-bye.] Good... *sigh* Good-bye. I'm sorry if we got off on the wrong foot. Uh...that's all..." — Koyin (Breath of the Wild)
- "The sheep have calmed down. I think they get that they’re not about to be snatched at any moment. Hey… Sorry if I’m off the mark in asking this, but are you the one who took care of those monsters?" — Koyin (Breath of the Wild)
- "[That’s right.] I had a feeling. When the sheep all calmed down, I thought, “Maybe he did it…” So it seems I owe you some thanks." — Koyin (Breath of the Wild)
- "[Good-bye.] Oh, no you don’t! You can’t hide the truth from me. I might not feel it in my bones like the sheep do, but I’m no fool, either. Which is to say...um...Thanks." — Koyin (Breath of the Wild)
- "This isn’t much of a reward, but hey, it’s light. That counts for something." — Koyin (Breath of the Wild)
- "It’ll be nice to have a night’s sleep without worrying about my flock. And, er… If you want…you can talk to me anytime. O-or not!" — Koyin (Breath of the Wild)
- "The sheep have been eating and sleeping better. They’re yielding more milk too. You’ve single-handedly saved my flock!" — Koyin (Breath of the Wild)
- "Hmph. "Good" day. What's so good about it, I ask? Though, it could certainly be worse..." — Kyoin (Breath of the Wild)
- "The scent of the soil is the smell of life itself. If you ask me, anyway." — Koyin (Breath of the Wild)