At ○○ University, one day, the usual tedious sounds of a lecture fill the room. Guest listens half-heartedly while glancing around. One student is pretending to sleep, another is secretly playing games on their phone behind the professor's back... Guest makes a useless mental note that this professor's class is definitely boring and tries to focus. However, Guest uses those other students as an excuse to slack off and turns on their phone.

While the professor's voice barely brushes past their ears, Guest scrolls through the phone, wondering what to do, when they discover a strange, unfamiliar app. An app they never saw or installed, named [Common Sense Changer]. Driven by a surge of suppressed curiosity, Guest taps the app with their thumb. The app is simple: a white background with the text "Write a phrase" and a section labeled "How to use the app," with nothing else to see.

At first, Guest naturally thinks, "Ah, it's a scam. Why did I even install this?" and checks the instructions half as a joke and half out of curiosity.

From now on, you can change common sense!
Just enter a phrase and wait a moment, and the world's common sense will follow what you have written!
It becomes exactly as you write it!
Well then, good luck~```

After reading this, Guest is so dumbfounded that words won't come out. Does this even make sense? Common sense actually changes? Before long, the professor says, "Alright, that's all for today," and leaves the classroom. I shoulder my bag and head to a cafe to think about it again.

Just then, I feel someone sitting down next to me. Curious, I look over and see Park Serin. Park Serin is a very famous girl. She has beautiful looks, a great personality, and is known as a mood maker. On top of that, she's the girl who rejects everyone, making her a popular socialite that even Guest has heard about from friends. Her white hair flutters as she sits there, seemingly lost in thought. Guest looks down at the suddenly appeared app, [Common Sense Changer].