Prompt from anonymous user on Tumblr. Note: Waka's bio says he has a much older sister. Since I don't think anything more than that has ever been noted about her, I decided to use her as I saw fit to make the story work.
"Ah, senpai! Sorry I'm so late!" Wakamatsu called out as he entered Nozaki's apartment. The rustle of plastic bags and the dull, tin thumps of canned drinks accompanied his voice.
"It's alright, Wakamatsu," Nozaki replied, getting up to help the younger boy with the heavy bags. "We had a few things that needed fixing, anyways. Only a few pages are ready for you."
Laughing quietly and thanking Nozaki for the helping hand, Wakamatsu greeted Chiyo and Mikoshiba while carrying bags to the kitchen. "My sister had come by for a visit. When I told her where I'd be going, she insisted on picking up some refreshments for us."
Nozaki nodded and put the large cans into the fridge so that they could get fully chilled again. "We appreciate it, we were running low. What kind of drinks are these? I don't recognize the packaging."
"She said it was a juice and energy drink blend."
"Mm, alright. That will help. I think it's going to be a late night."
"I'll thank her again next time we talk."
The two went back into the main room, setting up to get to work. An hour or so had passed, and Chiyo set her things down to shift back and stretch. Looking at the time, then the pages left in front of her, and everyone working hard, she hummed in thought. "Nozaki-kun?"
"Hm? What is it, Sakura?"
"Since there's so much left, were the others going to spend the night?"
"I was gonna," Mikoshiba answered, taking her cue to stretch out after so long hunched over.
Wakamatsu nodded, still concentrating on his work, "Yeah, probably."
"There's your answer, then. Why do you ask?"
"Well, if they're staying, maybe I should, too. That way we don't have to worry. If it's a group, it shouldn't be a problem, even if I'm the only girl. ...Right?"
"Mm, I don't see why it would be. I have more than one futon, enough for everyone to have their own."
"Okay! Then, I'll call my parents and let them know!"
She got up to make her phone call privately, and when she came back from getting permission, everyone had moved to take a short break for snacks and stretching. A few more hours of work and four stiff necks later, they breaked for dinner. Sitting in front of the television, they sipped at the drinks Wakamatsu brought, figuring it would be best to get those energy drinks in them before returning to work.
"I've never had any kind of energy drink...," Chiyo remarked when the can was half empty, staring at it and trying to read the label, finding her vision difficult to focus on the words without squinting. "I think it's too strong for me."
"Mm, I usually drink coffee and tea for all-nighters," Nozaki replied, frowning as he looked at his own empty can, jiggling it faintly and staring at it with a slight frown. "I've never felt so flushed from caffeine before."
Wakamatsu leaned forward worriedly, cursing faintly as he leaned too far and lost his balance, almost spilling his drink. The swear from the normally overly polite boy had everyone looking over at him with shock. He laughed nervously and rubbed the back of his head, quickly turning his attention back to finish the drink and hoping they would stop looking at him that way. Mikoshiba stood up and grabbed the three empty cans, looking down at Chiyo as she finished hers off as well.
She went to hand it from him, pausing a moment when something on the can caught her eye. "Eh, what's this, seven percent...?" Frowning, she pulled it closer, ignoring the impatient look and twitch of fingers Mikoshiba gave her as he stood there waiting to have the can handed to him. She squinted at it, yelping loud enough to make him drop the two cans that had been tucked against his side with his arm.
"What is it!?"
"It's... alcohol..."
"Wha...!?"
Wakamatsu shook his head sharply, getting up and going to pick up the cans Mikoshiba had dropped. Looking them over, his shoulders dropped as he realized she was right. "I didn't know... Ahhh, I didn't think my sister would do something like this! I'm sorry, I'm sorry, I'm sorry!" He shifted back and bowed frantically, tears in his eyes as he apologized.
Nozaki seemed somehow unfazed by the news, taking Chiyo's can from her and looking it over. "Huh. So it is. Interesting."
"I'm sorry, senpai!"
"It's alright, Wakamatsu. You didn't do it on purpose."
"But, but, but because of me...! We can't do anymore work tonight like this!"
"Ehh, speak for yourself! I can work fine!" Mikoshiba growled, his face flushed as he lifted his chin stubbornly and carried the cans to finally wash them out and put them in the recycling.
Chiyo shook her head, holding her hand to the side of her face and getting derailed a moment by the cool feel of her own skin against her heated cheeks. "Ah. I don't think I can, though... I could barely read, I don't think I could stay in the lines..."
"I see. Well, it's alright. It was an accident, after all."
"But, your deadline, senpaiiii!"
Poor Wakamatsu, he was outright crying now. Chiyo shifted over and patted his shoulder, murmuring simple phrases like "There, there" to him.
Nozaki shrugged and simply went around, gathering up the papers and making sure the manuscript was properly put away. "Don't worry about it, Wakamatsu. I'll just ask for an extension. These things happen."
"But not like this!"
"It's fine."
"It's all my fault! Senpai! I'm sorry!"
Sighing, Nozaki walked over to the stereo, checking what he had set to play before turning it on. After a couple of seconds, their school's Lorelei's voice came from the speakers. Wakamatsu promptly passed out, his knees folded under him as he sprawled forward. Chiyo laughed nervously and shook her head, standing up to carefully help Nozaki move the low table out of the way. Mikoshiba came back from his side trip to use the restroom and helped them get the beds laid out.
The work went somewhat slowly, as each of them dealt with their inebriation in their own ways. Chiyo very carefully and deliberately did every little action, things taking much longer but at least getting done right. Mikoshiba wasn't in as good of condition as he had bragged earlier, and his work was sloppy and tossed together. Nozaki, damn him, seemed completely unfazed! He had claimed to feel flushed, but he didn't seem impaired in any way. Chiyo couldn't figure it out, was he just very good at hiding it, was the effect just not yet noticed, or was actually totally fine? She supposed it made sense, how much larger than the rest of them he was, but it just wasn't fair, either!
Nozaki and Mikoshiba moved Wakamatsu into one of the beds, and Chiyo cried out when Mikoshiba dropped the sleeping boy's legs from waist high. All that happened was that Wakamatsu grunted in his sleep and turned his head. Nozaki set him down and they got him covered and lying on his side, a bottle of water and a shallow bucket beside him, just in case.
"Eh, well... It's good that at least he's asleep, but I don't think I will be for some time."
"Hey, where'd the manuscript go? I said I could still work."
"You couldn't even set up a bed right!"
"What!? It's perfectly fine, look!"
"The mattress isn't flat, the pillow is crooked and the blanket's tag is at the top!"
"Maybe the pillow is for my feet!"
"That doesn't even make sense!"
"B-Be quiet! It's fine! I'm fine!"
"Please stop shouting, both of you," Nozaki asked, shaking his head at them. They each pouted and crossed their arms, looking away from each other like they were children in a schoolyard argument, pretending the other didn't exist. "Mikorin, we decided to put the work off, and I'll ask for an extension. It's fine."
"Well, alright. But you know I had it just fine!"
"I know."
"As long as you know."
"I do," Nozaki finished patiently.