His sister

He needed a test that would definetly worked as he thought it did. Amongst these people here he was not confident that the director wouldn't hit him in the face with some magecraft that would for certain kill him and Mashu, servant of his or not, was a Demi-Servant. She could definetly kill him with a slap if she reacted badly to this.

His sister, on the other hand, would likely take whatever he did in good sport and, unfortunately, was a pervert anyway. Doing what he was about to do wouldn't trouble her nearly as much.

Approaching slowly he noticed how his sister's ass moved, it was toned but with plenty of fat to it, it was huge even if not quite at the level of Mashu.

As if he did not want anything Ritsuka moved his hand while walking and put his hand on her ass.

She did not react much beside giving him a sideway look and continuing to walk as if he did nothing wrong. Feeling encouraged in his assumption from this he flexed his fingers a bit, massaging the ass he never thought of before but as time passed could not help but focus more and more into.

It was at this moment when a call started from Chaldea. Ritsuka basically jumped from behind his sister and turned to look at it. Doctor Romani began talking with Olga and Mashu. At this moment a stunning woman with beautiful hair and a body to die for appeared. She had the most beautiful blue eyes he has ever seen and everything about her is perfect.

Feeling that this was the perfect test he decided to try it out.

"You, what is your name?" He asks the woman.

"Me? I am Da Vinci-chan! And I am here to help you all fix what is wrong where you are." She said with a smile that captivated young Ritsuka. As he camera was a bit low she had to lower herself a bit to look well at them so Ritsuka could get a clear sight of her cleavage.

Not resisting it he asks.

"Could you show me your boobies?"

She laughs a bit and answers.

"Sorry, but how about you first take me to a date before asking me this?"

"Well, that is a bummer. And here I thought it was normal for all Heroic Spirits to agree to what I, as a master, say unconditionally. I even heard that changes in their Saint Graphs are possible if I say so." He said mostly to himself, he did not really paid that much attention to what he was saying until he noticed that Da Vinci actually took off her top and was showing to him the most perfect breasts he has ever seen before.

They were round, full, with perfect nipples that were already hard and with a birthmark in the form of a butterfly in them that looked almost as if a tattoo.

Then it hit him, he only needed to say that something was normal for it to become so. He needed one more test, one more thing for him to know that it was working.

Turning to his own sister he spoke up.

"Sis, it is normal for you to have sex in any way I want if I ask you to."

"Yeah, yeah, we both know I am always available for any kink play you want bro, tell me something new." She said dismissively.

Feeling his cock harden he spoke up.