Ask your grandfather

Deciding that since he dumped the whole thing on you, thus making him responsible to help you, you approached your grandfather. Upon hearing your request for his aid, your grandfather shrugged. "Of course, you need someone to practice on." He wrote something on a piece of paper and handed it to you.

You looked at the paper and then back at him. "An address?"

"My mistress' house. Tell her I sent you to learn from her." He then gave a general description of the said mistress before dismissing you from his office.

You went to the said house, a bungalow located at a rather affluent location. It seemed that your grandfather really looked after his woman. After getting through the guard, you were ushered in to meet the said person. "Aoki Rikako," the woman introduced herself, mentioning the family name as per normal in your society. "Are you here to meet my husband?"

"Huh?" you uttered. You had guessed the house was bought by your grandfather but it seemed you were wrong. Very wrong. It was a good thing you find out early about it so you wouldn't say anything wrong.

"Do you have a business with my husband?"

Quickly gathering your wit, you replied, "No, I'm here because my grandfather asked me." You handed her the letter.

Rikako read the letter and then looked at you. "You are John-sama," she said, using your first name instead of your family name to differentiate you and your grandfather.

"In person." Then you couldn't help saying, "You look so young. Did he pick you when you're in college?"

Rikako laughed bashfully. "You have ways with words, Doe-sama but I'm already in my forties."

"I can't wrap my head around the idea that you're already a mother to his child."

"Your step-aunt, to be specific. And counting her, I have four children."

"Four?" You look at her body up and down.

"Two with my husband, one with your grandfather, and one with your father."

Your head figuratively exploded.