"Just hormones"

The 'girl' smiled, "did you hit your head or something? I look just like always! Or are you talking about the manly pecs in your hands?~"

"So, you truly are a guy?"

"Well duh! Cutting the pranks for a second I just developed in a very uncommon way, I can prove to you I'm a man if you dare lift up my skirt~"

"W-WHA-"

"Nishishi! So naive!" The mastermind laughed. "I dress like a chick because it confuses people, but don't let this totally-awesome silhouette fool you."

"So your body just... is like this... And you dress like a girl on top of it to match and confuse people... Why?"

"Why? For kicks obviously! Well, that and it's easier to always have the upper hand in every interaction when people can never tell when you're being serious about if you're a man or a woman."

"Huh?"

"Well, duh! Being the ultimate supreme leader isn't an easy feat! Misdirection and lies are really helpful to keep everyone around you confused, and that makes people easier to... direct~"

"I never thought you messing with people and pranking around had an actual purpose..."

"I'm smarter than you think sweetchi~ Better watch out!" The boy laughed.

"...how does being a girl play into it?"

"Hm? Well it's not like being a girl is part of a master plan, I didn't get to pick that part now did I? I will admit, it's far easier to confuse and take advantage of boys by acting all cute and flirty Nishishi!" He seemed proud of himself. "But it's not like that is my main tactic, I'm a mastermind, not a bimbo like Miu."

"Well... With a normally erotic body like yours I'd expect you to use every dirty trick in the book to seduce others..."

Shuichi could feel the weight on his hands change, as he could feel the slowly expanding body of Kokichi push against his attempts to be groped. Overall, her new shape had a small bit of chub that begged to be squeezed. With a mischievous grin, the boy turned around, swaying his ass in a seductive pendulum. "Oh I can do that too, never thought you'd be the kind of pervert to fall for a woman's charm so easily~"

The detective's hands went immediately to her ass, pulling her in closer.

"What are you doing?! Such an immoral act between men!" He shouted, clearly pretending to be offended, after which he laughed. "You won't find any contraband there Columbo. Are we done here?"