It was common knowledge that cold chapped your lips quickly, so naturally, Hiyori brought a few extra chapsticks with her for their group trip into the mountain. She didn't want Yato and Yukine's lips to chap and bleed, but also she didn't know where Yato had been and wasn't keen to let something that had touched his lips also touch hers.
She had seen the man drink vinegar, she didn't even want to know what other kinds of horrors had entered his mouth.
Unfortunately, as was apparently her curse, she kept finding out.
"Oh, Hiyori, is that chapstick?" Yato asked happily when she took it out to apply to her cold lips.
"Yeah," she said, already reaching for her pocket where she'd stowed the one for Yato, only for him to reach out while she was distracted and snatch hers from her hand.
Hiyori watched, as if in slow motion, as Yato extended the lip balm as far as it would go and chomped the thing right out of the tube before passing it back.
"Thanks," he slurred, "my lips were starting to hurt."
Hiyori watched, mouth agape in mixed fascination and disgust as Yato proceeded to use his tongue to plaster the munched on chapstick over his lips.
An exaltation of horror wheezed from her lips, unbidden by her mind.
"What the fuck?"