Ichika's apartment was small—a studio with a tiny kitchen and a bathroom too small for a tub.
Rin, having confiscated the phones, didn't sit in the living room. He went into Ichika's bedroom. He knew that being hovered over makes it hard to focus. Plus, if he sat there playing on his phone while they studied, it would be a bad influence.
The bedroom was already messy after one night. Luggage was half-open, and pajamas were tossed in a corner. Rin cleared a spot on the bed and tossed her laundry into a basket.
He opened his phone to check the "Baumkuchen" account. He looked at the comments for the "Short Boy, Big Girl" 4-koma manga he'd drawn for Shinju, then checked LINE.
His private messages were full. Aside from daily chats, Marin had sent several cosplay photos—not just mirror selfies, but high-quality shots taken by Misaki. Marin's poses were often provocative, featuring wide-legged squats that left her crotch clearly visible, though the focus was on "character accuracy." Misaki, on the other hand, sent photos in high-intensity fetish gear, like a cow-print bikini.
Rin saved them all immediately.
Ami also sent "spicy" selfies, like wearing her school swimsuit during swim class. Some were regular, others were shots of her small, pert ass, or pulling down the neckline to show her budding pink nipples. Sometimes she'd set up a tripod and film herself and Maki "playing" together—the sight of two petite girls "generating power" together was a total taboo-fueled rush.
Knock, knock.
Rin locked his phone. The door creaked open, and Ichika's sly face peeked through. Seeing him on the bed, she slipped inside and closed the door.
"Knocking on your own bedroom door?" Rin teased.
"I was worried you were doing something 'notorious,' Rin. I wouldn't want to scare you and have Kaede hold a grudge. This is a real JK's room, after all."
Ichika knew he wasn't the type to masturbate to her underwear—he preferred "parties"—but she liked teasing him.
Rin turned serious. "Student Ichika, do you have a question?"
"Yes, Professor!" Ichika stood at attention. "I have a very important question!"
"Proceed."
"Professor! What did you do to Nino, Miku, Yotsuba, and Itsuki? Haha!" Ichika broke character and laughed. She sat beside him, glancing at the door. "Seriously... how did you get them to actually study?"
She knew her sisters. They didn't have that kind of drive. And Nino, who had been barking at him two days ago, had just handed over her phone without a fight.
"It's a secret," Rin smirked. He couldn't exactly tell her he'd kissed them all to the point of climax and was using it as leverage.
"Ehh... tell me." Ichika leaned in, her breath hot against his ear. "If you tell 'Big Sister,' I'll let you kiss me~"
"Get lost," Rin pushed her away playfully. "You'll find out eventually."
Ichika pouted and held out a workbook. "How do you solve this?"
"Let me see... it's a basic formula. You have to split it into two parts... look, you're straining your neck. Just sit on my lap."
The room was too small for a desk. If Rin looked at the book, Ichika couldn't see. He pulled her onto his lap. Having practiced intimacy for their "acting" under Kaede's direction, sitting on his lap was second nature to her now.
Rin wrapped his arms around her waist to hold the book, explaining the problem. The heat of her body was pleasant. After finishing, he noticed her ears were bright red.
"Did you get that?"
"Eh... yeah, totally!"
"Liar. If you got it, explain the process back to me."
Unlike Mashiro, who could memorize anything even while being "poked" from behind, Ichika was too flustered by the physical contact to absorb a word. She stammered, unable to answer.
"I'll explain it one more time. Listen closely..."
While Rin tutored Ichika, Nino made a face at the bedroom door. She whispered to her sisters:
"Hmph... 'Math problems'? More like 'Physiology problems'!"