Think about the gentan modern au my friend and i made like a year ago. Tanjiro in a nurse, he finally finished his studies but he doesn't have enough to get his own place, neither can Nezuko, so they live on the apartment of their very nice, rich childhood friend Zenitsu, he was meant to get a business mayor since he is the heir of his Gramp's company but he lied, he isn't doing that.
Tanjiro's dad left him his car, it is old, but Tanjiro takes care of it like it is his child, it is his most precious belonging, he literally loves that car, absolutely no one can drive it and he doesn't trust anyone with it, would kill Zenitsu if he brings ice cream inside again.
Of course the car breaks down and Tanjiro is losing his mind, he goes to a mechanic someone recommended and hey? Does he knows that guy from somewhere?
Genya and Sanemi works for an old man that owns a car repair shop, Genya is a college drop out, they aren't doing well at home economically since his parents are not around, so now he works at the shop full time and spends the rest of his time taking care of his siblings. Except for that day he went to a night club, kissed a cute guy and drove him back home on the guys car.