chi-chi tells the others all the details.

“It had actually started when goku found out about the androids.” Chi-chi began telling the women present about her time with gohan as her lover. “”Goku never has sex when he’s training for a big fight, so when he started training to fight the androids I knew I was in for three years of celibacy.”
“Ouch. I can’t imagine going that long without sex. Fortunately for me vegeta gets even more excited when he trains for a fight.” Bulma interrupted chi-chi quickly but number 18 stopped her from saying anything else.
“Be quiet bulma, I want to hear this. Go on chi-chi.”
“Well after three years I can’t tell you how much I masturbated. I was pleasuring myself practically every night, sometimes twice a day. Then that fatefull day finally arrived and the guys left to fight those horrible androids, oh sorry number 18.”
“It’s all right Dr. Gero was a dork anyway.”
“Well as you know goku caught the heart virus and when he recovered from that he immediately went off to train to fight cell. Then he died.”
Chi-chi paused as she said this the memory was still painful even though goku was later wished back to life.
“Well that night is when it happened, that’s when gohan and I made love. That night I couldn’t sleep I just lay in bed crying at my lost goku. Gohan heard me crying and came in to comfort me. Well I was just a wreck my nightgown was all wrinkled up because of my tossing and turning in bed and it had ridden up to my thighs. Gohan blushed when he saw me and because of the way I was laying he definitely saw a lot of me. But he politely just turned his head and sat on the bed to talk to me. We talked for a long time at first we told each other how sad we were but gohan said we should think about all the good times we had with goku how happy he made us and how much he loved us. I was starting to see just how mature gohan had become. It was not just how strong he was he was caring and loving and it seemed all he wanted was to make me feel better. That’s when I looked at him in a way no mother should look at their son. He was sitting on the bed beside me in only his sleeping shorts and at tthat moment he reminded me so much of his father. When he reached out to hug me I held the hug much longer than I should have.”

(Authors note: Switching to a different point of view and to a present tense now. I hope this does not confuse anyone.)

Gohan was in bed trying to sleep, but having no luck. He had beaten cell earlier that day and saved the earth from destruction but the price had been very high. His father, goku, had died in the battle and later refused to be wished back to life with the dragon balls. Although gohan respected his fathers decision he still missed him very much. Gohan decided sleep was impossible and got up to get a drink of water and something to eat. As he passed his mothers room he heard her crying softly, no doubt she was trying to not wake him. His heart broke as he listened at his mother’s door and he heard her crying as much as he missed his father his mom had to miss him even more. Gohan slowly opened the door to go inside and comfort his mother. His mother was lying in bed wearing one of her very light nightgowns and gohan could see right up her legs and to her womanhood by the way she was lying on the bed facing away from him. He blushed and turned his head away but walked in to the room anyway.
“Mom? Mom, are you all right?”
“Gohan (sniff). I’m sorry honey I didn’t want to wake you.”
“You didn’t mom. I couldn’t sleep either.”
Gohan sat down on the bed as chi-chi sat up from lying on her stomach.
“I really miss him a lot mom.”
”So do I honey.”
“We have to try to remember the good times we had with him, all the fun he was.We cant dwell on the bad things, dad wasn’t like that he would want us to be happy. If we only remember the good times then it is kind of like he isn’t really gone at all.”
Chi-chi smiled at gohan and put a hand over his knee.
“I will always remember how dad was after a big fight mom. He would always celebrate with a really big meal and he always liked to have our friends over.”
Chi-chi blushed as gohan said this.
“Yeah and I always had to do the cooking. But that wasn’t the only way your father liked to celebrate.”
“What do you mean mom?”
“Well, Lets just say that after his friends went home and you went to bed he and I would have a private celebration right here in our bed.” Chi-chi started to get a far away look in her eyes as she was talking.
“Goku never wanted to make love when he trained for a fight so when the fight was over he was always very excited and he would make love to me for hours on end.”
Chi-chi subconsciously started rubbing her hand up and down along gohan’s thigh. The longer he trained for a fight the more passion he felt, actually the more passion we both felt. Goku used to joke that I was a super saiyan in bed. The longer I went without the more passionately we made love.”
Gohan was speechless, his mother had never talked like this to him before and the fact that she was in a sheer gown and rubbing his thigh had him getting an erection before he knew it.
“Uuhhh mom?”
Chi-chi seemed to snap back to reality and realized that she was rubbing her son’s thigh getting very close to his obvious erection. Chi-chi had been so sad about goku dying that she had not realized just how horny she was, three years of celibacy was a long time. She looked at gohan and suddenly saw much of his father in him, letting her desire and lonliness take control chi-chi made a fatefull decision. Chi-chi did not stop rubbing her hand along gohan’s thigh instead she moved it higher to lightly trace the length of his erection through his shorts.
“You’re a lot like your father gohan and I never realized just how much of a man you have become. You were right earlier, your father would not want us to be sad he would want us to be happy and to take comfort in each others arms.”
Without another word chi-chi leaned over and kissed gohan lightly on the lips. Gohan was stunned, His mother was seducing him! He could not deny that his mom was very beautiful, he had seen her briefly before when she had come out of the shower and he never did quite get the image of her naked body out of his mind, but he never in a million years would have thought that his mom would want to have sex with him. Gohan quickly got over his surprise though and not being a fool he started kissing his mother back.
Chi-chi pulled back from gohan and got off the bed, standing before her son.
“Are you sure you want to do this?”
Gohan and chi-chi asked each other this question at the same time, prompting both of them to laugh and answer at the same time as well.
“Yes.”
Which prompted another round of laughter from the two of them. Gohan hung his head and blushed a bit though.
“Uh mom. I’ve never done this before. I don’t really know what I should do.”
Chi-chi smiled at her son and tried to comfort him.
“That’s o.k. gohan I’ll show you.”