This is an idea that was gestating in the back of my head for a few months, and was only written in the past couple of days. It's a usual "happier Evangelion AU", of the type where Shinji lives as Misato's adopted child but in a normal setting as opposed to a happy AU in the show's status quo or one where he lives with his birth parents a la that alternate reality in episode 26.
The setting is inspired by the Japanese TV show Midnight Diner, a drama show about a diner open late at night where the nameless owner makes "comfort food" for his customers, whose lives he (and the viewers) bear witness to.
Misato's immediate reaction when the idea was broached to her was instant dismissal.
"Absolutely not. I don't want him working somewhere like that."
Kaji and Ritsuko tried again.
"He's been there with you plenty enough," Kaji pointed out. "And it fits his skill set."
"He needs to get out more. It's not healthy how shut-in he is." Ritsuko argued. "And it's not full-time. This is only four nights a week."
"I don't want Shinji working in an environment like that!" Misato retorted. "I don't want my-my son working in a back alley hole-in-the-wall rubbing shoulders with whoever walks in the door!"
Kaji raised an eyebrow. "You think so little of my place, Katsuragi? And of my clientele?"
"Misato," Ritsuko said. "It's in your precinct. You know it's not a bad part of town. Your officers are the ones on the streets there. And you know the owner-" She jerked her head in the direction of Kaji. "-well." She grimaced. "Very well. And Shinji needs to get out more. It's not healthy for him."
"The world…isn't kind to a boy like Shinji," Misato said softly. "He's so sensitive and quiet, he's such a good kid but he gets nervous around people and doesn't quite understand them. He likes it with just me and Pen-Pen."
"I know," Ritsuko said. After all, she had been the one to diagnose Shinji as on the spectrum .
"It's…it's not that I want him to avoid human contact forever…" Misato continued. "But the apartment is a safe environment he can control, and I don't know if it's right to force him…."
A few years prior Shinji had become less and less able to handle school. Misato had reluctantly pulled him out with Ritsuko providing a doctor's note. Shinji completed high school online, and early.
"Misato-" Ritusko began.
"He's a baby!" Misato shouted. "My baby! I can't let him…I…just…."
"He's nineteen," Ritsuko deadpanned.
"Exactly!" Misato said. "Practically a child!"
"Katsuragi." Kaji said firmly. "I won't push him. I won't let my customers push him. I won't let him push himself too far. This will be good for him. He's a good cook. It'll be a good paying job, four days a week. He'll get out and talk to people in a safe environment."
Misato was quiet for a minute.
"If something happens to him…" she eventually said.
"I won't allow it." Kaji promised.
"If something does, I'll kill you."
Kaji owned a small diner in Tokyo's Shinjuku district. Open four nights a week, from midnight to seven in the morning, its menu read only "pork miso soup combo, beer, sake, shochu." Despite this, Kaji would make whatever his customers requested provided he had the necessary ingredients.
Misato and Kaji had been an on-and-off item for several years before she had adopted Shinji. When the two weren't taking time off from each other, Misato would occasionally visit the diner. Sometimes she brought Shinji along as a way to both give him a break from always cooking at home and to get him out of the apartment for just a little bit.
Shinji was nervous at the prospect of starting a job there, not because he disliked it but because he was nervous about a job in general. Misato said it was something he should try for at least a few weeks before backing out if it wasn't a good fit.
But he was also interested. He loved cooking. Kaji was cool to be around (as much as his mother insisted otherwise). Shinji knew, deep down, it was wrong to keep hiding away from the world as a NEET at his age, and was honestly grateful Misato and Ritsuko were forcing him to do something he wouldn't do on his own otherwise. And besides, a modest income atop his weekly allowance would give him more spending money on books and Gunpla kits.
Shinji arrived at 11:17 P.M. the first night he was to work at the diner. Kaji met him and Misato outside.
"Katsuragi, Shinji, yo!"
"Mr. Kaji," Shinji smiled back. Misato narrowed her eyes and held Shinji's hand even tighter.
"I'm glad you were able to be here early." Kaji said. "We can start on meal prep and I can show you a few things I want you to know."
"Shinji," Misato said. She turned to face him, placing herself between him and Kaji, and put her hands on his shoulders. "You have my number. If you feel you can't handle it, call me."
"Yes, Miss Misato." Shinji said. He smiled softly. "But…I think I'll be okay tonight. I want to give this a chance."
"Remember, Hyuga and Aoba are working the desk tonight at the precinct-I've ordered them to be over here if you call them because something's wrong."
(This constituted a violation of the rules on conflicts of interest but none of the subordinates of Captain Katsuragi, Tokyo Police, were dumb enough to challenge her where her son was involved.)
"And you have Ritsuko's number too." she continued. "Just in case. Okay sweetie?"
"Okay, Miss Misato."
"And, whatever you do…" she raised her voice a little. "If that man behind me attempts to give you advice on women, you are to ignore it and call me immediately. Is that clear?"
"Yes, Miss Misato."
She pulled him into a tight hug and kissed his forehead. "I'll pick you up in the morning. Have fun. Work hard. Remember, I love you."
"I love you too, mom." Shinji said.
She let him go, ruffled his hair, and turned to Kaji. She folded her arms across her chest.
"I'll be here ten minutes before you close tomorrow morning. I expect my son to report that you did not attempt to instruct him in the ways of the unshaven lothario. If he says anything to the contrary, I will make life very uncomfortable for you."
Kaji's face didn't change from his relaxed smirk and he simply held up his hands in a placating gesture. "I'll take good care of him, Katsuragi. I want him to enjoy working here."
Misato sniffed. She turned and kissed Shinji on the forehead again before walking off.
"So!" Kaji said. "C'mon in, I'll get you an apron."
"Y-yeah," Shinji said, smiling nervously. "I'm looking forward to this, Mr. Kaji."
I have a few ideas for what stories to tell in this setting, but this is mostly a story that has no intention of "going anywhere". The nature of Midnight Diner's setting and using it as a vehicle for an AU means I can bring other characters from stories I like in and have Shinji interact with them. This is also posted on Ao3, and there I've tagged it as both AsuShin and KawoShin because I don't intend for this to be a story where Shinji ends up with anyone, just to explore him interacting with people, so I plan to tease romance fluff with both the Tsundere and the Twink.
Shinji being Misato's happily adopted child is a dynamic I love. Momsato best mom.
The vague implications in the background-Ritsuko's Shinji's doctor/therapist of some stripe, Misato is a policewoman, Shinji's a shut-in because of troubles at school that happened after he was adopted (likely from an abusive situation, because uh fuck Gendo), are all partly inspired by the long running KawoShin fanfic "Clarity"-give it a read, it's pretty good.
The diner's location, the juxtaposition between its stated menu and what Kaji actually cooks, and its hours are all taken from Midnight Diner. The only alteration is that the show doesn't seem to indicate it closes some days but I've changed it to a four-day work schedule to make it more realistic in that it gives Kaji and Shinji the ability to have a life outside of the diner where they can be awake on a regular schedule.