He found the manual

When he was in the locker room minding his own business organizing not only the data sheets but his own thoughts, he was also influencing her personality. But that didn’t mean he rewrote her entirely, as the manual dictates that the other two pedestals are there for other facets to her personalities. Her own stuff kept her ‘normal’ enough to notice any faults in her behavior. Then Hikigaya happened and now they’re in this mess.

Once he got out and closed the door, Yuigahama should have returned to normal but she was still conflicted. And investigating the locker revealed why. He opened the door, it felt heavier but was still manageable. They probably needed to grease it after.

It was just as he left it, except for a brochure right in front of the door. He picked it up.

“Mentality locker — a refined take to the mentality pedestal? User’s are given three lockers — each define a facet of subject’s ethos. Turn the school jock into the nerd? Make the exchange student the class clown? Make a terror prof into a meek friend? The possibilities are endless and the good news is it only expires after a weekend (two days). Well that solves most of our issues right? Huh. For a more hands-on approach: become the ethos itself? Awfully cryptic.”

Yuigahama’s makeup was in one section, her hobby’s were in the next, but the last one had a little journal packed with essays.

Unfortunately for Hikigaya, it was partially his fault. He may have left the closet with the school data sheet but he unintentionally left his essay in the last pedestal.

That explained her knowing most of his secret essays he shared to no one. Yuigahama had gained the knowledge of his journal thanks to this pedestal. But what else could Yuigahama know? When he was in the locker, she had acted odd like a parody of Hikigaya. There was no way she could have acted like him in the first place unless she was hiding the acting skills the theater club missed out somehow.

Unsure on how to solve this, he decided to experiment.

He removed the journal first. After, his hands carried the collar, burnt cookies, and toys into the last locker. Then he moved the makeup into the last locker as well. What was the best way to learn how this worked? Look for the mistakes and correct things after the trial.

He was basing this of Yukino’s description but Yui acted like a mismash of herself and Hikigaya Hachiman (that’s him). All her memories were mostly Yui while her personality played off both hers and his. So what would happen if you put the person in the locker inside the first one?

He really didn’t need to know but morbid curiosity was the mother of invention for loners like him after all— that was necessity for normies.

Well, only one way find out—

“Ah but it’s gonna be hot in there, better ditch my jacket.”

He undressed down to his undershirt and left the clothes by the door. He took a deep breath and made his way into the As he was about to close the door, a soft voice called out to him sending shivers down his spine.

“What are you doing, Hikigaya-kun?” Yukino asked ever the skeptic.

“… nothing. Definitely nothing nefarious. Don’t give me that look, Yukinoshita.”

“You were planning to do something to Yuigahama. Your rotten eyes can’t hide the truth.”

Better to come out clean than delay the inevitable.

“Oh okay, I figured out what’s going on with her. You see this supply closet — these lockers?” He pointed at the lockers, his pointing finger directed at the name tag on the entire thing. It had Yuigahama Yui written all over it. “So apparently they define and alter the person in the most literal way. Like say I add a baseball in that locker room and Yuigahama apparently becomes the best batter you’d ever seen or if you left books in there then she wouldn’t be botching her midterms like right now. So when I ended up in the last locker, she got influenced by being me and acting like me. But it’s definitely not harmful in the long term… I think.”

“So why are you undressed?”

“I got curious, if the last locker influenced her that much — turned her into a kindred soul, how much would me being in the first locker do? Would she become me?”

“… I don’t think I can handle another you Hikigaya. And don’t you think you should ask Yuigahama this before messing with her head once more?”

Hikigaya realized how foolish he had been. What was he doing trying to play with his friend? Was he being influenced by the room? Or was his morbid curiosity getting the better of him.

He did not have the time to rectify is his uncalled for behavior — a strong gust of wind somehow knocked the door shut lunging him into one locker and Yukino into the next.

“Hikigaya!”

“What the hell—“

The door slammed.

Everything went black. He tried to scream but nothing came out.

Then a flash. The sunlight from the window hit him— hit him while he was in the closet? No, he was back in the clubroom. His heart rate was rapid and he couldn’t shake off the uneasy lump in his throat. His chest was also heavy, like something was attached to it—

He looked down.

Big fat tits!

“Huge…”