Author's note: I do not own Genshin Impact.

This fanfiction is set after the events in my other fanfiction, How To Get Diluc And Kaeya To Co-operate, but it's really just a birthday one-shot for my favorite redhead. Enjoy!

Kaeya left the Knight's Headquarters with the nagging sense that he'd forgotten something very important. My Vision is here… Bennett didn't burn my cape on our adventure today… I already gleaned some important information on Treasure Hoarder movements from the reports today… What could I possibly be forgetting? He paused at the top of the steps; brows knit in an uncharacteristic frown. Well… it will come to me. He started moving again. I'll drop by the Angel's Share to see if I can pick up any more info from loose tongues.

He entered the tavern quietly, his eye darting to the counter in search of familiar blazing red hair, but finding only Charles. Concealing his disappointment, he scanned the rest of the room and spotted a pair of Fatui seated at a table near the back. Nodding a greeting to the bartender, he slipped off into the dark corner and found himself a seat near the Fatui. Within a few moments, Charles brought him a Death After Noon, already long familiar with the Cavalry Captain's habits.

Kaeya sipped the chilled beverage and opened his Adventurer's Handbook, pretending to be engrossed in the Enemies section. His keen ears were tuned to the Fatui at the next table.

"I sure wish this place had Firewater. It isn't a proper tavern without it," one of them complained. Kaeya resisted the urge to defend his brother's tavern.

The other Fatui shrugged. "Even if it's poorer quality, be glad you're in here drinking this stuff tonight."

Cocking his head quizzically, the taller Fatui set his drink down and asked, "Why tonight?"

Out of the corner of his eye, Kaeya noticed that the shorter Fatui was a bit older and guessed he was a veteran taking a newer recruit out for a drink to give him some basic information. The man shook his head. "Every year, our forces suffer heavy losses on this night. No one knows quite what's going on or why it happens, but camp after camp is decimated until dawn. It's not safe to be deployed around these parts at this time of year."

The recruit scoffed and chugged another gulp of his drink. "Sounds like an urban legend you tell to newbies. I'm not falling for it, Grandpa."

Shrugging, the older man leaned back and crossed his arms. "Believe it or not, I don't care. But don't wander outside the city walls tonight. You won't live to regret it."

Kaeya lost track of the conversation, preferring to sift through what he'd heard. Tonight? What makes tonight so- He drew in a sharp breath. Oh. He couldn't believe he'd forgotten. Rising swiftly, he abandoned his cool glass and wove an elegant path through the busy tavern until he reached the bar. "Charles, not that I'm not glad to see you, my dear fellow, but where's Master Diluc tonight? Doesn't he usually man the counter at the start of the week?"

Charles shook his head respectfully. "No sir. Not this week. I'm not sure where he is, but he never comes into work in the last week of April. He always pays me overtime, and gives me fair warning, though. Oh, right, I forgot!" He leaned down under the counter, sorting through something. "He asked me to give this to you when you came in tonight. Ow!" He banged his head on the counter as he stood up. Rubbing the spot gingerly, he held out a note.

If you're interested, I'll be at the cove below Stormbearer Point.

-Diluc

Kaeya barely remembered to give Charles a nod of thanks before he whirled and vanished out the door.

"That ridiculous fool… He should know better than to be out hunting Fatui by himself!" Kaeya fumed under his breath, sprinting through the darkening streets. "He's going to get himself killed!" Some logical part of his mind reminded him that for four years, Diluc's entire life had basically consisted of hunting Fatui by himself. The thought of returning to that period, rife with mounting worry at every day that Diluc failed to reappear… Kaeya shuddered and threw himself into running as fast as he could.

He spared a second to offer a hurried salute to Swan and Lawrence at the gate, but didn't bother responding to their surprised looks. There was no time to waste.

Kaeya prided himself on keeping his body in excellent physical condition so as to be prepared for any emergency, and it paid off now. He could run further than any other knight, and he pushed himself to his limits as he raced through the dusk falling over Mondstadt.

Staggering out of the woods and onto the beach an hour later, he paused to let his body recover for a moment, and to search for that elusive fiery head of hair. Still nothing. Dragging in an extra-large breath, he started off again.

It wasn't until he got further down the long stretch of sand that he spotted the smoke rising from a nearby campfire. He angled his path towards it, making sure his sword was at the ready as he neared the cheerful flames.

A lone figure was perched up on a high rock, back to the fire, gazing out to sea. Telltale scarlet locks escaped from the person's hood, making him instantly identifiable.

"Diluc!" Kaeya gasped, his stamina at an end. He staggered over to the rock while his brother turned to stare at him in surprise.

"Kaeya?!" The tall redhead jumped down from his perch, grasping Kaeya's shoulders to steady him. "Calm down, are you injured? Who attacked you?" Diluc's eyes blazed. "I'll finish them myself."

Kaeya grabbed Diluc's wrists, stalling him as he caught his breath. "No, *huff* no attacks. *huff* I'm fine, just, hah, winded."

Diluc scrutinized him closely before releasing his shoulders. "What's wrong? Why were you running?"

The tall Cryo user swallowed, his heartbeat falling into a more relaxed rhythm. "I got your letter from Charles, and I was afraid you were going to get yourself killed attacking Fatui camps by yourself."

"That's it?" Diluc blinked at him. "You nearly ran yourself into the ground because I left a letter for you? I didn't even fully expect you to come, if I'm being honest."

Kaeya rolled his eye, exasperated. "I overheard a couple of Fatui in the tavern tonight, talking about how they sustain heavy losses on this night every year. I didn't put it together until I remembered what today is." Diluc stiffened, but Kaeya finished softly, "I forgot it was your birthday, Diluc."

Diluc crossed his arms and turned away, looking out over the sea again. He didn't respond.

"Hey." Kaeya set a hand on his brother's shoulder.

"I'm not going back to town, Kaeya. Not tonight." Diluc's voice was brittle.

There was silence for a moment. Kaeya's mind raced, trying to come up with something, anything, that would stall Diluc. Finally he landed on an idea. It made him sick to his stomach, but he steeled himself against the sensation and spoke anyway. "I'm not asking you to. But… I haven't really told you about my childhood. Before I met you."

Disbelief made Diluc spin around. "What?"

Kaeya shrugged. "Well, I figure we can spend the night one of two ways. Either we can go hunt Fatui until dawn and probably not feel any better about ourselves, or we can sit here and I can tell you all about my sordid past in an effort to distract you." He hauled himself up on the rock and patted the spot beside him invitingly.

Diluc stared at him, scanning his face as if to verify that Kaeya wasn't teasing him as usual. Then the edges of a reluctant smile curled his lips. "No need for such drastic measures." He braced his arms and pulled himself up next to Kaeya. "How about I tell you about my childhood instead?"

Oh. Kaeya winced, ever so slightly. He really didn't want to talk about his life before he became a Ragnvinder, but he wasn't sure that hearing about Diluc's no-doubt charmed childhood would be much better. "Well…"

"Or I can go back to hunting Fatui," Diluc offered breezily, making as if to jump down.

"No no, we can talk about you as a kid!" Kaeya blurted hurriedly, snatching his brother's arm. Then he froze.

Diluc was laughing. Kaeya's thoughts splintered, only one remaining. I can't remember the last time I heard him laugh. The tall redhead collected himself and grinned at Kaeya. "Come now, my childhood can't be that intimidating," he teased.

Disoriented, Kaeya made some sort of dismissive motion. "Um, sure, go ahead," he said ever-so-articulately.

Diluc settled himself into a comfortable position before looking up at the stars. "Well, when I was young, I was a bit of a rascal sometimes. One time I took my brother on a tour of Mondstadt. Father was quite pleased with me until he learned that we'd gone rooftop hopping with our gliders in a restricted zone. We were lucky no one caught us."

Kaeya blinked at him.

"Another time, just after I got my Vision, my brother told me to start a campfire in our hideout so we could roast marshmallows. It got… a little out of hand, and we wound up burning down half the vineyard." Diluc looked totally relaxed, leaning back on his elbows with his boots crossed. "Father forgave us eventually, but he made my brother carry a few spare Cryo potions in his inventory after that. It was a good idea, I suppose… I don't believe we ever told him how close we came to burning down the Knights' Headquarters when we were spying on Grand Master Varka that one time."

Slowly Kaeya realized what Diluc was doing. Every story he retold involved Kaeya. Not a single one came from the time before Kaeya's entry to the Ragnvinder family.

"When Adalinde began to teach us our letters, it was a bit of an adventure. I remember declaring that the letter 'D' belonged to me and refused to say anything without a 'D' in it. Adalinde wasn't thrilled, and she was even more irate when she discovered that I'd convinced my brother to claim the letter 'K.' He had the worst of it… there are quite a number of words with the letter 'D' in them, but not quite so many with a 'K.' Adalinde banned us from tongue-twisters for a month after that." He smiled fondly at the memory.

Slowly Kaeya said, "One time… I told my brother about the mysterious island to the east of Mondstadt." Diluc looked him, surprised, but fell silent. Kaeya continued, "I wanted to go explore it, but it was too far away for us to swim there. So in the morning of my ninth birthday, he woke me up early, and dragged me out of the house with him. I had no idea where we were going until we reached Starsnatch Cliff that afternoon. 'We're going to glide there!' he told me excitedly. I didn't understand. I asked him why we were going, and he looked at me like I was crazy. 'Because you wanted to go explore it! It's your birthday, and I'm your big brother, and it's my job to make all your dreams come true!'" Kaeya swallowed hard. "I knew then that he was going to be my best friend in the entire world."

Wordlessly Diluc reached over and gripped Kaeya's hand firmly. After a moment he laughed. "If I recall correctly, we never did make it there. Father found us just as we were about to launch ourselves off the cliff with the wind against us and a target far too distant for two children to reach."

Kaeya chuckled. "You're right. But to me, it didn't matter if we made it there or not. What mattered was that my brother was willing to do it for me."

"Of course! I remember another time…"

They stayed on the rock for hours, reminiscing about their childhood together as brothers and best friends. Not once did Diluc bring up Kaeya's origins, and Kaeya never brought up Diluc's birthday.

Finally, as the first rays of light began to stream across the sea, Kaeya stretched. "Well, I think I've had enough storytelling for one night." He sat up straight and jumped down off the rock. He looked up at Diluc and smirked. "You ready to head back, sleepyhead?"

Diluc yawned, then leaped down beside him, his Darknight Hero disguise fluttering in the wind. "Not quite yet." He turned back to the sea. "I have a promise to make good on."

Kaeya joined him and stared at the tiny island veiled in small swathes of mist. "You want to head out there now? You know your overheated Pyro body temperature melts my ice, right?"

Diluc gave him a rare smile. "I know. That's why I asked Lumine to bring me that." He pointed further down the beach to another large rock.

"A rock. You asked our Honorary Knight to bring you a rock," Kaeya deadpanned.

Huffing, his brother started off down the beach. "No, I asked her to bring me a Waverider."

"What? All the way from Inazuma?!" Astonished, it took Kaeya a moment to catch up with Diluc. "How did you manage that?!"

He shrugged. "Easy. I paid her quite a bit of Mora, a few bottles of my best grape juice, and a full meal at the Dawn Winery whenever she choses. Unsurprisingly, Paimon agreed immediately."

Kaeya laughed. "You sly fox! You've discovered the trick to recruiting our Honorary Knight: Mora, food, and making sure Paimon is within earshot when you make the offer."

A smirk tugged at Diluc's mouth. "Quite right." He rounded the rock and stood beside the boat, raising a brow at Kaeya. "Ready to make good on that dream of yours?"

Kaeya swallowed hard, staring at Diluc for a moment. Finally he said, "Of course, Dawnbird."

"Oh, and Kaeya?" He waited while Diluc fidgeted with his gloves before looking up. "Thanks for coming. And talking. It… it helped." Dawn's light landed on the face of Dawn's owner, bringing the depths of his relieved smile into sharp focus. "I'm glad you're my brother."

Kaeya's smile was more genuine than any that he'd given in years. "Me too, Diluc. Me too."