She wakes and thinks she is dying.
The skin between her thighs is thick and sticky, glued together, scratchy where it stretches. It's an alien sensation. For a moment she thinks she may have soiled herself in her sleep, but it feels sicker than that. A feeling builds in the pit of her stomach, aches that crest along the ridges of her spine and between the hollows of her hips.
— rot
You remember the first time you bled, soaking through your trousers unaware, and the urgency with which Vadhe hurried you away from your playmates. You remember picking your way through the briars in the wood to wash your rags in the faraway hidden stream. Encountering your neighbor there, turning away from each other and scrubbing in silence. The disgust curling your father's lip when he noticed a stain on your sheets. Hot shame floods you and you hang your head.
"Oh, dear" Pearl thought loudly. Then she looked at Connie, standing in the middle of the room, eyes streaming, lower part of her body more red than anything and arms wrapped tightly around herself. Pearl's heart broke at the sight of her student, and she took two quick strides and enveloped her in a gentle hug. "Oh Connie" she whispered quietly as she stroked Connie's beautiful dark hair. "I know you must be scared, but it's alright. It's OK. You're going to be fine. Have this happened before? Do you know what this is?" at Pearl's compassionate words, Connie shook her head and then started to cry, leaning against Pearl's thin chest.
Pearl's heart swelled with compassion and warmth at the trust Connie was putting in her at this moment. She remembered her own surprise when something similar happened to her around the level of physical maturity as Connie was now. How Rose had sat her down and talked about the multi colored visitor (blood color depend on gem color). She knew it must be a little different for humans, but her library had prepared her. In fact she had thought she would have 'the talk' with Steven about sex and things. 'Oh dear, maybe I'll have to later today', she thought to herself.
— Steven Universe fanfic "Echoes"
"It's hopeless! It's already hopeless! My stomach hurts so strangely!! Blood... blood is coming out! It's so scary! I don't want this! If this continues, I'm going to die!"
— Chespin, Pokémon Super Mystery Dungeon doujin Strawberry Moon Pie
"THIS SUCKS, I HATE BEING A GIRL, THIS SUCKS, I HATE BEING A GIRL, EVERYTHING FUCKING HURTS, WHERE IS ALL THIS BLOOD EVEN COMING FROM, FUCK THIS FUCK THIS FUCK!!!!!"
— Amy Campbelle, No Nuts November by The Transformistress
