"How about a story about a character who discovers a hidden world or society?"
Technically Senpai is discovering a hidden world - the real world, because he's lived in the digital world his entire life.
Okay, I know Tac is like, a mouse, but...uh...just go with it.
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After Senpai was let free in the world, it was up to Ruby and Keith to guide him around. But they had no control when Senpai went to highschool for the first time. They could only hope he wouldn't mess things up.
At Maginage High, Senpai found himself lost among the huge crowd. Sure, he was usually alone in Senpai Highschool Crush Kiss Kiss Dance, but the players were enough to keep him company. Now he really had no one.
At lunch, he had no one to sit next to. He didn't eat anything in the digital world, so his hunger was still a strange feeling to him. Humans had to do so much to just stay alive, like eating food and drinking water. Senpai, having lost his appetite, opted to take a walk around the campus and explore the building.
He found himself behind the school, where a chain-link fence separated the school grounds from the forest. There was a strange creature sitting against a tree, reading a book. He looked like a honeybutterfly breed. An unfinished box of sandwiches, probably his lunch, lay near him. He was alone. Senpai thought this was his chance to make a new friend and walked towards the honeybutterfly.
"Hey there, I'm new to this school and I don't really know anyone...will you be my friend?"
It had only been a few days since Senpai was freed, and he didn't know how to make proper conversation yet. Luckily the honeybutterfly's reaction was positive. He laughed at Senpai's words.
"Uh, sure! It must be confusing 'cause it's already the middle of the year."
The honeybutterfly dropped his book so he could pay attention to the newcomer. Senpai was surprised how easily he was willing to be his friend.
"I'm Tac, how 'bout you?"
"Huh? Oh, I-I'm Senpai," Senpai stuttered like a fool.
Tac let out a light laugh. "Don't be so nervous! Starting at a new school can be confusing, but you'll get used to it. Hey, what school did you used to go to? Was it in the area?"
Senpai froze. He didn't want to tell Tac that he had destroyed the entire world in an alternate timeline and had never gone to school before, except for Senpai Highschool Crush Kiss Kiss Dance's pixel high school, and he didn't learn much there because Ruby kept spending all her points on charm rather than intelligence. He was afraid of breaking his newfound friendship with Tac. Luckily, the bell rang, signaling the end of break.
"I'll see you tomorrow!" called Tac, taking a bite of his leftover sandwich before getting up and walking to class. In his haste, he left his book behind.
"Wait, your book-!" Senpai started, but Tac was already gone.
Senpai kept the book in his backpack, vowing to give it back the next day, and ran to class so he wouldn't be late.