Legend of eating mermaid flesh was primarily gotten from Takahashi Rumiko's wonderful series, the Mermaid Saga. It's shown up a few other places as well, but that's the most well known.
The only way to kill one who has eaten the flesh of a mermaid is to cut off their head. No Highlander references intended. *Grin*
By Icka! M. Chif
"Conan-kun? Are you alright?" Ran asked. She looked concerned.
"Come to the lab." Hiabara said. "I have something to show you."
"Not really." The small boy looked out the window, watching the city's twinkling lights. His glasses were resting beside him in the window ledge. The city seemed alive under him, and yet at the same time, so distant.
"You found a cure?"
"Is there anything I can do?" Ran asked, stepping closer. He could feel the warmth radiating off of her, melting some of his numbness and shock.
"No. Something else. You'll have to come and see."
He paused, looking hesitant. "Can I... Can I have a... hug?"
"Alright. I'll be there."
"Of course." Ran picked up the small boy and sat down on the chair he had been leaning on, cradling him against her. He gave a shuddering sigh, his body relaxing against her.
"I'm here." He said, walking into the lab. "What's so important?"
The girl said nothing, content to wait as she ran her fingers thru his hair. He shuddered, wrapping his arms around her neck and holding on to her as if she was a lifeline.
"I made an important discovery about APTX 4869." Hiabara turned to grin at him. "Something you won't believe."
"I'm sorry, Ran." He whispered against her shoulder. "Sorrier than you could ever know."
"Like what?" He walked over to the computer monitor.
"For what?" Ran turned to look at him. "Did you eat the rest of the cookies in the jar?"
"I think I may have discovered why the drug didn't kill us."
"No." He shook his head. "Something far worse."
Ran smiled. "Like what?"
"Have you ever heard the legend of eating mermaid flesh?"
"I can't be Shin'ichi for you anymore."
"Sure. If you eat the flesh of mermaid, you're supposed to gain immortality. What's that got to do with APTX 4869?"
The girl flinched, drawing back to get a better look at the despondent boy. "What? Conan-kun, what are you saying?"
He looked up at her, his eyes bright, almost feverish. "If you could live forever, would you?"
"You're not making any sense!" Ran became alarmed, resting her forehead against his. "Are you ill? You don't have a fever..."
"APTX 4869 was based on an unknown poisonous sample. I only recently discovered what it was." Hiabara said calmly. She then snorted, giving a small bitter laugh. "...The remains of a mermaid."
The boy gave her a slight smile. "I'm not sick, I promise you."
"But they're a myth!"
"You didn't answer my question." The boy pressed. "If you had the chance to be immortal, would you take it? Never age, never grow old, never die?"
Hiabara gave him a small sardonic smile. "I assure you, it's quite real. And both you and I have tasted it."
"I... I don't know. I don't think so." She shifted him in her lap, so that his head was resting against her heart. Had it been a different time, he would have blushed from the close proximity. "It would be rather lonely, living forever. Watching everyone around you die."
"One in a thousand people can eat it and become truly immortal, Edogawa. Maybe less. To the rest, it is a deadly poison."
"Hmmm." The boy listened to her heartbeat. "I suppose you're right."
"So you're saying we're immortal?!" He asked, taking a step back. Logically, he understood what she was saying. Realistically, it didn't make sense. And yet, at the same time it made terrible sense.
"What brought this on, Conan-kun?"
Again with the smile. "No. We are not. You are."
"I have to leave soon." He whispered sadly.
He shook his head in denial. "You've got to be joking, Hiabara! Someone can't turned be immortal!"
"Your parents are picking you up?" She asked, resting her head on his.
"It's all in the facts, Kudo." Hiabara began counting them. "You haven't aged, you heal faster than a normal person and that bullet back in the cave should have killed you! It all makes sense."
"No." He wrapped his arms around her waist. "I'm going alone."
"Kids heal naturally fast, it's a scientific fact!" He retorted, something in him resonating. Fear? Realization?
"You're too young to wander around by yourself." She replied. "I'll go with you."
"It took you only a few days to completely recover from getting shot. It took me weeks before could walk without the crutch after I got shot." She retorted.
He waved it off. "Other things can contribute to that. Eating the mermaids flesh is a myth. Myths aren't reality!"
"How much proof do you need, Edogawa?!" She pulled a knife out of her lab pockets. He quickly backed up, his hands held up in an appeasing gesture. "Will your eyes suffice?!"
"Because you'll die." The boy's tone was much too sad, much too old for one his size. Like he had aged decades since she had last seen him that morning.
There was a quick flash of steel, and pain from his left hand. He stared in numb shock as he realised that his pinkie finger had just be cut off. Hiabara picked up the loose appendage and held it in front of him, before placing it back on his hand.
"I can take care of myself." She retorted. "I've been taking care of you and Dad for a while now, remember? And I'm a karate champion."
He could -feel- the finger re-attach it's self to his hand. He curled his hand into a loose fist, examining what should have been an injured appendage.
"You'll still die. One way or another."
There wasn't even a scar.
The boy looked up at her. "Promise me something?"
"I... but..." He sighed, reality sinking in with a sickening lurch. "What about you? You took the drug as well."
"Like I said, it was synthetic mermaid's flesh." She gave him a bitter smile, wiping off the bloody blade. "Just as it's taken a while to turn you immortal, it's taken a while to finish killing me. Different people react to it differently. I didn't beat the odds."
"Forget about me. Forget both of me. Both Edogawa Conan and Kudo Shin'ichi."
He let out a breath. "How... how long?"
"Both of you? Conan-kun, what are you talking about? Why should I forget Shin'ichi and you?" Ran started to get upset. Something was seriously wrong.
"A few hours. Two, according to my calculations. Maybe three. Then I'll start to mutate and the drug will finally kill me."
"Because I want you go on in your life. I want you to be happy."
"Happy?" The breath caught in her throat, sounding suspiciously like a sob. "Why would I be happy?"
A cynical smile and a dismissive wave. "Don't waste your pity on me, Edogawa. It makes sense in the end, does it not? The symmetry I was looking for when I took the drug in the first place."
A small hand reached up and caressed her cheek. "You're beautiful, you know that?" His voice sounded both young and old at the same time. "I do love you."
Hard eyes looked at him. "But I'm telling you this for a reason. You need to leave."
She swallowed, covering his hand with one of hers. "Shin'ichi?"
"Why?" He demanded. "What's going on, Hiabara?!"
"Yes." Familiar eyes in a too young face nodded. "I'm sorry, Ran."
"Imagine what would happen if the Organization discovered the secret of APTX 4869. Immortality in a pill." Hiabara looked serious, like the Ops member she once had been. "I can't let that happen."
An explosion from outside rocked the building. Sirens began to wail as the sounds of people shouting echoed thru the streets.
"Ai? What are you going to do?"
In the distance, a pillar of smoke and fire rose from the direction of Shin'ichi's old house.
"I'm taking all of the information about APTX 4869 and it's results with me when I go. Agasa Hakase is out of town for the week, he'll be fine. All that is left is the one loose end."
"That would be Hiabara." He said softly. He knew that somewhere else there was probably another explosion, bigger than this one. Hiabara was nothing if not through.
"After I'm gone, The Organization will most likely figure out who and where I've been, which means they'll find you too. You're going to have to leave, hide somewhere else."
The boy regretfully slipped out of her lap. "It's time for me to go."
"You have until then to say good bye to anyone you wish. After that, they'll most likely be monitored. To contact them is to risk their lives."
"Shin'ichi?!" She stood up to follow. There was a slight prick on her arm, and she slumped back down in the chair, fast asleep.
"You'll have to be careful, Edogawa. Humans are jealous, petty, vain, selfish creatures. They fear anything they don't understand. And Death is the ultimate unknown."
The boy re-arranged her to a more comfortable position, then gently kissed her cheek. "You're right, Ran. It is lonely."
"I understand, and thank you." He turned to leave. "Good-bye, Ai. I hope you find your sister."
"Farewell, Edogawa. Safe journey."
Silent as a ghost, the boy picked up his backpack and glasses, and then slipped out of the house, leaving the sleeping girl behind.
He nodded and left the building for the last time. There was nothing left for him there.
Without a backwards glance, he disappeared into the crowds on the street. No one noticed the small boy threading his way thru the confusion.
Kudo Shin'ichi was dead.