How Do I Find Work After the Apocalypse with a Civil Engineering Degree?!

[Temporary blurb. A lighthearted, semi-realistic construction-infrastructure novel set in the Stone Age, with a reverse harem and female-oriented romance.]

Someone asked: What career prospects are there in the sunset industry of civil engineering?

I answered without hesitation: The world has to end, of course!

I never expected that the day after I made that joke,

the world really would end.

Me: "..."

Is this right?

Hello, I'm an utterly ordinary civil engineering student with terrible luck. To survive, I have to work eight jobs at once: delivering food in the morning, making milk tea at noon, playing games for other people in the evening, and occasionally working part-time as an exorcist, among other things.

The day I finally saved enough money to buy a home and lie flat, I clutched the property deed I'd worked so hard to get and lay down on the bed in my shabby little room. That's when I saw a green beam of light cover the entire world.

The bad news: I was petrified, and all my hard work had gone to waste.

The good news: The world had ended, so it was time for civil engineering's spring to arrive!

The moment I finally broke free of the petrification, I was all set to roll up my sleeves and show what I could do. But the first thing I saw was a weird head of hair, green fading to white, like a giant scallion.

...Could this be a side effect of petrification? Should I give him a haircut first?

That guy just picked at his ear and said, "Oh, you're awake. Great. Now help me rebuild the world!"

I feel like I've been dragged into another huge pit, but I can't put my finger on why.

At first, me: Heh heh heh, us civil engineering grunts are back to roll up our sleeves and take over!

Later, me: I have something to do today. Someone's dragged me off to be a workhorse. I want meatballs...

*Stone Age reverse harem romance, with multiple love interests. Haven't decided on the point of view yet. A crossover with a few other series. Lots of complicated elements, lighthearted style. It's a science series, but the realism of the infrastructure-building is completely unscientific (?).

*The protagonist is an extremely unlucky college student who's already started her internship. She's young, rather gloomy, but when it comes to work she's very good at mooing away like a little workhorse. She has an offbeat sense of humor and likes to make snarky remarks.

*The blurb title says "civil engineering girl," but the plot may call for a mix of civil engineering, architecture, environmental studies, landscape design, design, urban planning, cost engineering, and so on. In short, she'll dabble in all kinds of construction-related fields. The idea is that she knows a lot, but it's no use (.). Due to the author's limited abilities, water supply and drainage, remote sensing, materials, and so on may not feature much. I'm not a professional, so please be gentle if you spot any errors.

*It won't be very long, and the science won't be rigorous at all. It just borrows the name of civil engineering. The infrastructure-building won't be realistic either. It's mainly romance and comedy.

Theme: Treasure every day you have money