The next appointment.

"Konnichiwa," Dr. Sugimoto greeted with a slight bow after she entered the examination room.

"Konnichiwa," Mari and her younger sister, Yuika, bowed.

"Oh, where is your husband, Mrs. Osano?" Shoko asked, noticing the young woman in a high school uniform sitting next to Mari.

"He could not make it," Mari explained.

"Oh, why not?" the doctor wondered.

"He had to go on a week long business trip to Shanghai," Mari sighed. "So I brought my sister, Yuika, with me for today's session."

"I see..." Shoko hummed, sitting down across from the two women. "What brings you here, Yuika-chan?"

Yuika looked at her older sister before speaking. "My sister asked me to come because she wanted me to share something with you..."

"Oh?" Shoko mused with arched eyebrow.

Yuika paused, averting her eyes with the doctor's gaze, before speaking. "I had sex with onii-chan..."

"Your brother?" Shoko gasped.

"Shouta, our brother-in-law," Mari corrected. "My husband's younger brother."

"He is like a big brother to me," Yuika explained. "He is a year older than me and is in university."

Shoko nodded, understanding the love triangle that was developing. She looked at Mari and asked, "Is this a problem?"

Mari bit her lower lip but did not answer.

"Yes... No, doctor," Yuika shook her head in confusion. "I love him... but as a brother..."

"Please explain how this situation came to be, Yuika-chan," Dr. Sugimoto asked.

"I... I..." the younger sister stuttered.

"Everything you say in this office is confidential between us," Shoko said in a soft motherly voice to calm the high school senior's nerves. "Not only am I medical doctor but a sexual therapist."

"Yes, doctor," Yuika nodded. She looked at her older sister for a moment before speaking. "One night I was pleasuring myself..."

"Masturbating," Shoko corrected matter-of-factly.

"...masturbating," Yuika blushed, "when I heard the door to my bedroom closed. I thought I had already chooses is so I went to investigate and found onii-chan standing at the door. 'What are you doing at a time like this?' He did not say anything so I grabbed his wrist and pulled him into my bedroom and closed the door behind us."

"So what did you do?" Shoko asked as she took notes on her tablet.

"I asked him, 'Were you looking?' and he shook his head. I did not believe him and said, 'Liar. Then what is that?' I pointed at his erection in his shorts."

"What did he say?" the doctor asked.

"He did not say anything because he knew he was caught," Yuika replied. "So I said, 'You got so hard seeing my naughty side. Do you want to see more?'"

"What did he say?" Shoko wondered.

"He nodded so I took him to my chair, I rolled down my underwear, and pulled up my t-shirt to reveal my breasts."

"Please demonstrate, Yuika," the doctor suggested.

"Doctor?" the high school senior gasped in shock at Dr. Sugimoto's unusual request.

"I need to know as much information as possible," Shoko replied matter-of-factly.

Yuika looked at her sister, who paused before nodding. Believing the two women knew what was best for her interest, the girl stood up to remove her skirt, rolled down her panties to her feet to reveal her bald pussy, and then pulled up her blouse to reveal her huge breasts.

Shoko took a photograph of Yuika for her files before saying, "Please continue."

"I sat down like this," Yuika replied, sitting down on the chair with her thighs spread apart, "and I started to masturbate in front of him." She started rubbing her wet slit with her left hand while holding her right leg with her other hand. "I then said to him, 'It is very embarrassing. Onii-chan, do it with me.' He started rubbing his hard erection in front of me."

"And then?" Shoko asked.

"He got very excited and grabbed my knees to spread my legs wide apart. He tried to enter me but I covered my pussy with my hand like this." Yuika demonstrated by placing her left hand over her snatch. "I protested, 'No, we cannot. We are not blood relatives but we are still siblings!'"

"What did he do?" the doctor asked.

"He pushed me back like this," Yuika answered, leaning back into the chair, "and tried to enter me again. I begged to him, 'No! See, if you do it like this it is like we are having sex!' and I grabbed his penis so it would like along my pussy lips instead."

"Interesting," Shoko hummed as she wrote down her notes on her tablet before she stood up to walk to a cabinet drawer to retrieve something. "A moment, please."

"Doctor?" both sisters gasped when Dr. Sugimoto turned around with a strap-on dildo around her.

"I want to recreate exactly what happened in the situation for my notes," Shoko replied, walking in-between Yuika's thighs. "Is the dildo as big as your brother-in-law's penis?"

The two sisters glanced at each other before Yuika shyly answered, "His is a bit longer and fatter."

"Interesting," Shoko nodded, noting that the dildo was already bigger than most Japanese men's penises. She placed the dildo on top of Yuika's pussy, letting the school girl grasp it, before she started rubbing the girl's slit with the length of the plastic shaft.

Yuika moaned while the doctor continued to rub her pussy lips and clit with the dildo until the girl let out an orgasmic cry with her left hand involuntarily releasing her grasp of the rubber penis.

Shoko saw the opportunity to slip the dildo into Yuika's dripping wet pussy.

"I screamed, 'No! Onni-chan, it is going inside of me! Stop!'" Yuika moaned as her pussy lips stretched wide apart by the thick shaft entering her.

"He did not stop and pull out?" Shoko asked.

Yuika shook her head.

The doctor grabbed the girl's knees to keep her legs wide apart and started stroking in and out of her pussy. Yuika laid back, grabbing the back of the chair while her massive breasts jiggled violently with each thrust her body absorbed. Her high pitch moans filled the examination room as the doctor accelerated her thrusts, bringing the girl to orgasm.

"Where did he cum?" the doctor asked.