Jealousy
It was a fit of frustration that had stemmed from the silliest of arguments. Perhaps the biggest problem with dating someone who was your best friend was that they knew how to press all your buttons. It wasn't anyone's fault that he was so irritated.
Karane mentioned that he was easy to fluster. That he took to jealously fast when it came to her. He denied it of course! And then happenstance led Link to walk by at that exact moment. In all her excitement to prove Pipit wrong, Karane reached out and caught the green clad teenager's arm.
"Link! Would you like to get some dinner with me?"
Honestly Pipit expected him to say no. That he was busy with whatever quest he was suddenly on. But he didn't. He gave her a smile and said "Yeah I was just about to grab some food! I'd be happy to."
Which resulted in Karane winning the argument. Pipit got jealous—immediately. He was jealous that Link had the time to have dinner with her, when he had to go out on patrol instead. Jealous that he didn't have time to take his own girlfriend out on a date. Jealous that Link had started growing into someone who could be considered far more attractive than Pipit.
"H-have a nice meal." It was stuttered, and flushed. What else was he supposed to say to that? Admit he was jealous? Never. He left them with a clearly forced smile and headed back to the sparring hall to claim his sword for the evening.
Which was where he was having his fit of jealousy—in private where no one could see. Pacing back and forth and pushing his hands through his hair and muttering nothings about how much better the blonde was than himself.
He didn't even notice the door open at first, or the red head walk into the room. It wasn't until she cleared her throat that he turned around and saw her, apple in one hand the other perched on her hip. Tapping her foot. A victorious smirk on her face.
"You seem a little jealous, Freckles."
He blushed an angry red and almost pouted at her, but instead took a few steps to pull her into a tight embrace. She dropped the apple in his sudden assault on her, but he didn't care. If she had intended it to be for herself he would replace it for her.
"Mine." The word was self explanatory, as he held her tightly to him.
It was incredibly easy to make Pipit jealous.
