"Dinner shouldn't take too long; I'll come out and call you when it's ready, okay? So, don't go too far, Izuku."

"I won't!" Izuku told his mum before scampering out the door, along the garden path, down the roughly-hewn steps and finally skidding to a stop by the beach and the rock pools, squeezing sand between his toes.

His smile was stretched from ear-to-ear as he settled onto his knees by the first pool, the shining water reflecting the still-bright sun. Seaweed gently swayed and touched the surface. Izuku leaned down and stared hard, trying to catch any hint of movement, then pouted and sat back. Nothing exciting in there, just a couple of snails and limpets. Well, he was still far from the sea – he'd definitely find something better further up.

Picking his way over boulders and doing his best to avoid getting his feet too wet, he clambered to a spot where a ridge of stone jutted out by the sea. He couldn't get here when the tide was too high, but right now it looked perfect, waves tickling the ridge without spilling over the top. That meant there would be lots of creatures stuck in the pool from the tide going out, right?

Sure enough, his shadow was enough to spook a shrimp and a fish into dashing away from him. He giggled and wiggled his finger in the water, another tiny shrimp revealing itself and disappearing just as quickly. But what about… Aha!

Izuku cupped his hands around a snail shell and lifted it out into the air, water trickling through his fingers until just the shell remained. He kept his hands still and waited. Just as he thought he must have been mistaken, there was movement. And then, a leg, cautiously creeping out and touching his palm. He gave a little squeal at the ticklish feeling as the hermit crab slowly emerged from its shelter, eyes like little periscopes moving in all directions.

"Whatcha got there?"

Izuku yelled and flailed, dropping the crab with a plop into the pool and falling backwards onto his hands. The animal scurried away into a nook, but Izuku could only focus on the wide-eyed stare of a blond boy, his head bobbing above the ridge and looking at him with raised eyebrows. His face broke into a grin.

"What, did I spook you?"

"Who—who are you? Why are you swimming here?"

The boy pulled himself up onto the ridge with his arms, his bottom half still in the water. "I'm Katsuki!" he said with triumph.

"Izuku." He thought he could see something orange behind him. His brows furrowed, then he gasped when he recognised it as a huge fish tail. "Watch out!" he cried, pointing behind Katsuki with a shaking hand.

Katsuki looked back. He broke out into laughter, saying, "Jeez, you're such an idiot! Are you kidding me?"

"What?"

"I'm a merman, stupid." He gave the tail a little shake to emphasise his point.

"Woah, really? That's…that's so cool!" Izuku crawled closer to him to get a proper look. His mouth fell open as he saw how the boy's chest turned into cream and orange-striped scales, all the way down to a big, spiny fin. "I've never seen a merman before. Do you live at the bottom of the sea?"

"Yeah-huh. In a big coral house, with my mum and my dad and a singing crab."

"You can talk to sea creatures?!"

"No, I made that last bit up. Obviously."

"Oh." Izuku tried not to let his disappointment show. "I like hermit crabs."

"Is that what you were looking at?" Katsuki rested his head on top of his folded arms, getting comfortable in his spot by the ridge.

"Yeah, I always come down to the beach when my mum doesn't need my help." He wound a bit of seaweed up around his finger absent-mindedly. "There are lots of cool things to see."

"Nothing as cool as me, I bet."

Izuku giggled. "No, nothing as cool as you. Except – oh! Once I found a shark tooth! But, wait, that's still not as good as you."

The boy grinned with a proud look in his eyes. A moment passed without either of them saying anything, each curious about the other.

"Izuku! Dinner's ready!" a distant call carried over to them.

"Oh, I-I have to go." Izuku twisted around, hesitated, then turned back to Katsuki. "Will you come back tomorrow and tell me more about the bottom of the sea?"

"Yeah, sure. You humans must hate being stuck up here all the time. It's so…dry," he said with a wrinkled nose. "It's the least I can do to add some coolness to your life."

Izuku beamed. "Great! I'll see you tomorrow, then, Kas—Katu—uh, Kacchan!" He scrambled onto his feet and started running back up the hill.

"What did you call me?!" he heard from behind him.

"By-ye!"


"And then he told me he'd come back tomorrow, and he's so amazing, mum, a real merman!" Izuku jumped up and down and yanked at his mother's dress as he gushed.

"That's wonderful, Izuku. But don't let your guard down, okay? You should be careful of the merpeople."

"What? Why?"

"They don't…understand us very well. Usually, they're very prideful and secluded. But…well, I'm glad to know he's about your age; I can't see the harm in that. I'm sure you'll make great friends." She ruffled his hair, then set down two bowls on the table for dinner.

The conversation drifted to the back of his mind as they ate, overrun by excitement and forgotten by the time he went to bed.


"So, why did you come here yesterday?" Izuku asked. He sat cross-legged on the ridge, with his elbows on his knees and his face leaning on his fists. Above him, clouds drifted lazily across the sky as it started to turn to dusk. He tilted his head at Katsuki, who was splashing himself with water so that he wouldn't be "so freaking dry."

"I was hearing all these stories about humans, and I had to see them for myself." Red, red eyes gazed at him. "I was just gonna look, but then I saw you were a kid like me. Heh, my mum gave me such an earful about running off on my own."

"Oh no, did you get in trouble?"

"Do you think I would be here if I did? Stupid Izuku. My dad said it's good for me to make friends, so if it's you, it's okay. Anyway, it was definitely worth it."

"Really?"

"Yeah. You're just as weird as all the stories say!"

"Kacchan, that's mean!"

He pouted. "Kat-su-ki."

Izuku opened his mouth to pronounce the complicated name but got too nervous about messing it up and closed it again.

"Are all humans this bad at saying words, or is it just you?" He put his hands on his hips, right at the juncture between skin and scales.

"Hey, there are lots of smart humans! My mum knows everything about sewing and plants and fixing stuff. She said I'll be able to do all of that when I'm her age, too." Izuku got up and pointed at his house on the top of the hill. It sat nestled in the middle of a fenced garden, made of white brick topped with a red tiled roof. "Look, she replaced all of the roof when the thatching started leaking with those tiles. It took her hours, but now it never leaks!"

"Thatching? Leaking?"

"Yeah, it used to be all straw, and sometimes, when it rained, the water would come in and get everything wet."

"Oh yeah, you don't like things getting wet."

"Nu-uh."

"Huh. I guess not all humans are totally useless…" Katsuki mumbled, looking down at his hands.

Izuku smiled and sat back down. "How far away is your coral house from here?" He tried to spy the seafloor, but he could only see the rocks descending into murky blue as if it were bottomless.

"About a ten-minute swim. Well, a ten-minute swim for me. I'm a super good swimmer."

"Wow! How fast can you get, um, over there?" Izuku gestured to a random spot in the open ocean.

"This fast!" Katsuki exclaimed before diving in. His tail created whooshing ripples of water on the surface, and a few seconds later, he popped out with his arms spread wide, metres away from Izuku. He laughed and dipped below again to swim back.

Izuku clapped him when he returned. "You're incredible, Kacchan!"

Katsuki's cheeks turned pink and he shrugged. "It's not a big deal." He cleared his throat and continued, "Anyway, if you're going to use a nickname, I should too. How about Deku?"

"I don't want to be called Deku!"

"Too late, you're Deku now."


"I'm starting to learn this awesome trick my mum knows. You wanna see?" Katsuki gripped his bicep with his hand, radiating confidence as he bobbed in the water.

"Show me! Show me!" Izuku urged. He leaned over the ridge until he almost tipped over into the water, catching himself at the last moment.

"Pssh, useless Deku. Okay, ready? Watch really closely. I gotta do it in the water."

"Okay, I'm watching."

Katsuki dipped below the surface, his tail standing out against the grey-blue sea. He coiled up his body, taut and patient, and then, in a flurry of bubbles and movement, shot out an arm at breakneck speed. A flash of white light burst from his palm for a millisecond. His head popped out, his gaze fixed on Izuku.

"Wow, Kacchan! That was amazing! But, um, what…was that?"

"You can't tell?! Don't you humans know anything?" he said with a roll of his eyes. "Well, mantis shrimp can hit stuff so fast that it creates a mini explosion in the water. My mum learnt how to do it and is teaching me now! When I get bigger and stronger, I'll be the king of exploding stuff."

"I bet you will!" Izuku said, shaking his fists up and down in his excitement. "You're so cool, Kacchan."

"Yeah, I know," he replied with a smirk. "I'm gonna keep practising it tomorrow. What about you?"

"Me? Well… We're going to harvest all of the vegetables and take them into the village market tomorrow. Hopefully we can buy some cakes while we're there!"

"Cakes? I've never had them before."

"What?! That's—!" Izuku started welling up. "Y-you've really n-never had cakes?"

"Woah, jeez, calm down. I bet you've never had our food either. You're missing out on some quality seafood, like salted tuna and seaweed pasta… Hey, why don't we swap sometime?"

He sniffed and rubbed his eyes dry. "That sounds good. It won't make me sick, will it?"

"No way!"


Izuku was most definitely sick after eating whale steak and seagrass. They decided not to swap food after that.


Izuku kicked his feet in the water, the waves lapping at his trousers where he'd rolled them up. Katsuki was lolling back, his tail flicking every now and then to make little adjustments. He heaved out a great sigh.

"What?"

"I'm bored." His head faced the sky; clouds reflected in his glassy eyes.

He knew what could liven him up. Izuku gripped the rock he was sitting on and jerked his foot in Katsuki's direction, sending a big splash onto his face. He giggled with delight.

Katsuki blinked, then focused on him, a sly expression on his face. "Oh, you wanna go there? Okay!" He twisted his body and slapped his fin down hard, a mini tsunami soaking Izuku in an instant. He shrieked and laughed and kicked his feet even more. The constant disruption of the water made it hard for the merman to get his own splashes to break through, even with his big tail.

Katsuki surged out of the sea and grabbed Izuku around the waist, grinning as he pulled him down under the surface. Izuku didn't have any time to react. A shock bolted through his body and he opened his mouth to shout, but only managed to let out a chimney of bubbles with increasing panic. Katsuki was still pulling at him, spinning him around, and Izuku was getting so disorientated he lost track of where up was, and he couldn't breathe, and he tried to break free and swim upwards but the water was slowing him down so much, and he didn't want his mum to be sad about him being gone—and then he breached the surface, sucking in a huge mouthful of air in between coughs.

He crawled onto the dry rocks with the help of pushing hands, salt stinging his eyes, his throat, his chest. He wanted to throw up but held back to get his breathing under control. He was shivering with cold despite the sun beating down on him.

"What the trench, Izuku?! Why didn't you tell me you couldn't swim? I can't believe you could be so stupid! You didn't think it would matter that you're useless in the water after all this time we've been playing together here? You really are Deku!"

Izuku pried his eyes open, saw Katsuki acting frantic and explosive. Great, gushing tears started flowing down his face unbidden and then he couldn't stop his sobs or his wails.

"D-Deku, you—!"

Izuku stumbled to his feet and bolted away up the hill, almost tripping more than once over the steps as he failed to wipe his tears away. Katsuki was shouting something at him, but the words were jumbled up in his head. His vision was still blurry by the time he collapsed into his house.

His mum gasped, rushed over and gathered him up into a cradling hug. Her gentle shushing and encouragement gradually calmed him down.

"It's okay, Izuku, it's okay. I'm here."

As he explained what happened, she started welling up herself, decrying Katsuki for putting her baby in danger like that.

"You don't have to see him anymore," she said, wiping her eyes dry. "You'll be okay."