Senku had gotten pretty good at diving for seaweed.

Well. Kind of. He still sucked at holding his breath…and gathering seaweed…and swimming…

Okay, maybe he wasn't good at it, but he'd gotten used to it. Fresh seaweed had a lot of benefits, even minimally processed (he had no time for anything but the bare minimum), so diving he went, even though he was still on his own and it probably wasn't safe.

He usually waited until the sea was calm as could be, not wanting to get caught in a riptide or something, before starting his little underwater expeditions. Like today—he'd done work near the beach so he could check on the state of the water every hour.

Finally, around sunset, the water seemed right. Eager to get the seaweed as soon as possible, he stripped down, grabbed his backpack-basket, and waded out into the water, then dove in.

The water was so clear and clean that finding heathy-looking seaweed was easy, and he quickly filled his bag to capacity, only having to come up for air five times (instead of the usual seven). He even grabbed some kelp, too.

Satisfied, he started swimming back to shore…

…or at least tried to. Once he noticed he was going backwards, he felt a cold panic overtake him.

He stopped trying to swim, focusing on just floating and observing. Sure enough, he was being pulled out to sea. Riptide. He looked around hoping for some kind of little outcrop he could grab onto, but there was nothing around him. Just water.

Could he use his backpack as a flotation device? Kelp had air pockets to help it float in the water, and he'd gathered some, so he quickly moved his bag to his front and clung to it like a particularly soggy koala.

And all the while, the land got farther and farther away.

Stupid. Stupid. He shouldn't have gone swimming alone, and definitely not at low tide, but what choice did he have? There was no one else alive! He couldn't ask someone else stronger to do this!

…he hoped that, if he died, Taiju either didn't wake up or somehow would figure out the nitric acid thing quickly. Being alone was hell, and Taiju wouldn't last long on his own.

But Senku would rather not die at all, so he focused on conserving his energy for the eventual swim back to shore. The swim that seemed to be growing longer and longer by the second…

He shivered, then cursed. Being completely naked wasn't helping him regulate his temperature at all. He probably wouldn't freeze to death, but it sure would make the swim harder.

Could he swim sideways to escape the riptide? He tried, for a good five minutes, before having to stop, already exhausted.

He trembled and glared at the waves around him. He wouldn't give up. He couldn't. He was the only chance humanity had at revival—almost eight billion people—and he wouldn't let them down! He just had to figure this out.

But the sea kept pushing him out. Finally, around a half a kilometer from the shore, it ended and he was free. No longer moving. But sure as hell not close to land.

His muscles were trembling. From effort? From the cold? Both?

He looked at the shore, hoping the riptide had spit him out somehow closer to a different part of it, but it all seemed equidistant.

Damn it. Okay. How was he going to get back?

Because there wasn't a scenario here where Ishigami Senku gave up. It would be a waste of energy to even consider it.

His legs were cramping. He forced himself to remain calm, not to scream at his own body for giving up on him. It hurt, it hurt, but he could push through it.

…he could. He had to.

He started kicking back. Waves were lapping at his shoulders. He held onto his basket of kelp and seaweed keeping him afloat, and he gave the riptide a wide berth, focused on getting back to land.

So what if it didn't seem like he was moving? His body wouldn't last until high tide pushed him in naturally. There was no debris around him to use. There wasn't a choice, so he kept kicking.

…he'd really wanted to see Taiju and Yuzuriha again, to find his dad…

And a wave crashed over him and he lost his grip on the basket, wasn't able to take a breath before he was pushed under.

He didn't know what way was up, which way to swim, and his lungs were filling with seawater, and he was scared—was this it for him?

But he'd never just lay down and die, so he tried to relax and see which way he was floating up, then swam that direction to the best of his ability.

His head popped above the waves—he coughed and hacked, desperate for air—and another wave pushed him under. And then another kept him down.

Human bodies couldn't function without oxygen. His body couldn't fight biology, not like this—

—his eyes struggled to stay open, his lungs not even bothering to try expelling the water—

—and he saw a glimmer of rainbow light, and thought it was nice that at least oxygen deprivation had made him see something beautiful before he died.

And the next thing he knew, he was waking up, blinking up at the sun.

Lungs didn't hurt. Legs didn't hurt. He felt great, actually.

Confused, he sat up.

And came face to face with a girl his age, completely naked.

Wait—was that a tail?

She smiled at him. Her teeth were all razor-sharp. Her ears looked more like fins, spiked fins like a lionfish.

"You," she said, her voice melodious, "are a very determined creature." She grabbed his chin with a cold hand. Her fingers weren't webbed, but they were tipped with wicked claws. "I've taken quite a liking to you, so I'll keep you. Can you speak?"

"What are you?"

She laughed and withdrew her hand, her claws brushing his throat. "A rude little creature! That's alright, I'll still take care of you." She flicked her tail. "I'm an amabie, of course."

Senku could see the tail that split into three, he'd obviously been healed, but weren't amabie supposed to have beaks? (He figured this was some kind of dream, his brain transporting him away from the reality of drowning, but he was still curious.)

"The better question is, what are you?" She pulled herself closer and he scrambled away slightly to avoid her bare breasts pressing against his chest. "I've never seen anything like you before," she went on. Her eyes flashed weirdly in the light of the setting sun—like a fish's, he realized—but it was a very human-like curiosity on her face.

"Human," he said, and she scoffed.

"Humans are ancient history. They died out thousands of years ago, so don't try to fool me."

He rolled his eyes. "Sure. And amabie are totally real. I know this is some kind of stress dream while I die, but I don't know why my brain decided to suddenly pretend that yokai aren't myths."

She tilted her head. "You're not dying, little creature. I rescued you." She put her hand on his chest and he shivered. "I saw you try so hard to get back to shore, how you never gave up. I couldn't let you die, not after all that." She hummed. "But it was very easy to heal you. It was supposed to be that way, when humans were alive…"

They looked at each other in silence, neither willing to believe the reality of what the other was saying.

…shouldn't Senku have died by now? What was taking so long?

…this couldn't be real.

…right?