"Miku!? Why are you hiding in the wardrobe!?"
Rin pulled the door open. The two sisters stared at each other in total awkwardness. Miku crawled out, her head hanging low.
"...."
Miku's face was scorching hot. She couldn't say a word. Rin suppressed a laugh, his gaze moving between the two.
"Don't be shy. You're both here for the same reason—to make sure I pass the test. Why don't I compare your differences right now?"
"...." "...."
Both girls bit their lips, enduring the shame. Coming to Rin alone for something lewd was one thing; doing it together was a whole different level of humiliation.
Rin sat them both on the edge of the bed. "Look up. How can I compare you if you're hiding? Next week's test is going to be harder. It'll be a problem if I fail."
Miku and Yotsuba's shoulders trembled. Finally, they raised their blushing faces, eyes brimming with tears of embarrassment.
"Who should I start with?"
"..." "..."
"Since neither of you is talking, I'll just have to compare by feel. Only by comparing can I know the difference..."
"Mmph!?"
Rin tilted Yotsuba's chin up and kissed her. Yotsuba froze, her eyes squeezed shut as tears escaped. Her lips were pressed tight, trying to resist his entry. But Rin's hands were busy. One hand stroked her back to soothe her, while the other moved down to her soft thighs, gently kneading her springy butt cheek.
A moment later, her hands moved to wrap around his neck. Her lips parted, welcoming him. The wet, slurping sounds of the kiss were loud in the quiet room. Her legs rubbed together. The atmosphere of Ichika's room was quickly becoming thick with lust. As Yotsuba got into the rhythm, Miku sat there awkwardly.
She didn't know where to look or what to do with her hands.
Luckily, Rin didn't leave her out for long. Once Yotsuba was thoroughly dazed and flushed, he let her go, a silver thread of saliva stretching between them. He immediately moved to Miku's lips. His scent was now mixed with Yotsuba's. Though kissing him in front of her sister was mortifying, Miku was more experienced with him than Yotsuba. It didn't take long before she forgot about Yotsuba and began responding passionately.
Yotsuba was proactive; Miku was enchanting. Even as identical twins, their reactions to being played with were distinct. Once they were both relaxed, Rin pulled back. Miku and Yotsuba's eyes met; the awkwardness had faded, replaced by a deep, shared heat.
Rin put on his "food critic" face, looking between them.
"Hmm... Yotsuba, Miku... both your lips and tongues are equally soft and delicious. I can't tell the difference at all." He paused, looking dead serious. "It seems I need to perform a more in-depth investigation."
In-depth... Yotsuba nodded, her eyes showing a hint of anticipation through the shame.
"Stand up. Put your hands up—like a 'banzai' pose~"
Yotsuba followed his instructions, revealing her smooth, pale armpits. Rin undid the ribbon at her waist and lifted the skirt of the white dress. His gaze traveled up her toned thighs to her white panties, then her flat stomach, and finally her large, swelling breasts.
Rin didn't stop there. He stood Miku up and pulled her dress off as well. Though they were still in their underwear, it was the first time they had bared so much of themselves to him.
"H-how is it?" Yotsuba asked, her eyes shining.
"Like this, I can see small differences." Rin reached out and touched their stomachs. Both girls gasped and held their breath. "Yotsuba, because you exercise, your core is tighter. Miku, you're much softer. But there's a more obvious difference than just feel."
Rin's smirk turned wicked as his fingers slid down. "Yotsuba, your body is much more sensitive than Miku's. You're already wet just from a kiss."
"Huh? Ah!" Yotsuba clamped her hands over her crotch, realizing he was right. There was a tiny dark patch on the fabric of her white panties.
Miku instinctively covered herself too, checking with a finger. She was slightly damp with excitement, but not yet soaked through like her sister. She felt a strange sense of relief.
"You can't cover yourselves. How am I supposed to study you? For the sake of the test..."
"Pervert..." Yotsuba whispered, but she tremblingly moved her hands away. Miku followed suit.
Rin wasn't satisfied with just looking through fabric. He reached out and unhooked their bras, letting their heavy breasts spill out. With the dresses and bras gone, the wet spot on Yotsuba's panties was glaringly obvious. Miku was starting to show a spot as well.
"Hmm... same size as Ichika. And the hair... also the same as Ichika. Sparse and soft."
They weren't completely hairless, but the hair was light, soft, and localized to a small patch.
"They look the same, but let's see if they feel the same... Hands behind your backs. Chests out. Yes, like that."
The two girls arched their backs, presenting their breasts to him as if they were offerings. Rin cupped a heavy, pale breast from each girl.
"The color is the same. But Yotsuba's are firmer, while Miku's are softer."
The white meat overflowed from his hands. Their nipples hardened and peaked under his touch, begging for attention. Rin didn't disappoint. He analyzed the color, shape, and texture, noting the subtle variations caused by their different lifestyles.
"Yes, very good," Rin said, still pretending to be "academic." "I have a good understanding of the outside now... Ahem. Next, it's time to check the inside."
"""!!!"""