When Doctor Grugger was conceptualizing this procedure, he thought that the transition from a male to a female would be much easier to pull off. Little did he know that there was a lot to consider in this procedure. Something he didn't account for was Ruben's undisclosed heart issues. While operating on Ruben, he suddenly had a heart attack. The doctor tried his best to revive the patient but it was too late and Ruben died halfway the procedure.
Considering that one of the patients died, the doctor decided to change trajectories with his procedure. He has a fresh harvestable body with him after all, and both of them are already legally dead. That's when he thought about recreating Ruben in Arianne's body. He knew that he cannot make an identical copy. Reshaping an 18 year old woman's body to that of a 45 year old man's is impossible even for him. But he can reshape Arianne's body to make it look close to what Ruben's looked like. It wont be identical but the resemblance will be close enough that most people would assume that they were siblings or cousins.
Doctor Grugger was fortunate with Arianne. He would have more difficulties if Arianne was a lithe and petite woman. Lucky for him, Arianne stood at 5'8 and had an athletic build. This already solves half of his issues as Ruben was only 5'10 so the height difference wont be too noticeable. The doctor took out all of Arianne's sex organs and replaced them with her father's. It was an intricate procedure but he was able to pull it off. While doing this, he also decided to transplant Ruben's beard to Arianne. Ruben had a black beard that covered half his face.
Arianne, as of right now, looks like a young woman. Attaching a beard to her will make her appear more like a man. He also cut Arianne's hair bald. The doctor also knew that he will have to keep her locked out for months so that the hormones will alter her body. While the doctor transplanted Ruben's sex organs to Arianne, he didn't really modify a lot to her body. The male hormones that are being pumped to her body (as well as her former dad's testicles pumping it naturally) will develop her body naturally to make it look like a man's body. The doctor estimated for this procedure to take at least six months, but he intends to keep Arianne locked out for at least eight to ten months.
After many hours of hard work, the operation is done. Arianne is now functionally a man and HE has the cock and balls to prove it. Now it's only a matter of times to make the hormones do their work to modify his body naturally. The doctor was watching his subject very intently while he was still strapped in the metal bed that he was operated in. All of the sudden he heard some light groans coming from the subject.
"Ughhhh where am I?"
"Good, you're awake. You and I have made a breakthrough discovery"
"What are you talking about? Where's my dad"
"Unfortunately, he didn't make it. You on the other hand are reborn as a new man" said the doctor. He rotated the metallic bed making it so that it was facing a full body mirror that showed Arianne what the doctor has done to her (now his) body. The most noticeable thing was that the crotch area was heavily bandaged as well as his chest. The presence of a beard is also very obvious along with the fact that Arianne was now bald.
"What the fuck did you do to me? You're a monster!"
"You can call me whatever you want, but what I have done is a breakthrough in science and medicine. You are now a fully functional male. Aesthetically, I will let the hormones to their work, but you have a fully functional penis courtesy of your now deceased father"
"You can't keep me here forever!"
"I know, and I don't intend to. I want you to reintegrate yourself in society as a man. But for the time being, you're staying with me while you're healing and developing as a man who is reborn. For the meantime, feel free to listen to this"
The doctor plugged in some headphones, forcing Arianne to listen to static audio. Little did Arianne know that this static audio was meant to disrupt his thoughts and wiping it clean for suggestions. The doctor intends to do this until his patient was under his care. New suggestions will be given once the patient is ready, but for now he's simply preparing for the second phase of his experiment.