Esper Harem in the Apocalypse

"Is there any way to stop me from doing that?" he asked curiously.

"Don't burn yourself out using your powers. Simple."

"That's common sense. I was asking if there is a way to stop this. Like, there could be times when I would need to go all out, you know? And during that time, if I worried about hurting others, I wouldn't be able to do that.

So I was wondering if you could provide me with a way or maybe some technique that could give me free vitality without killing or hurting anyone," he asked calmly.

After a moment of silence, Nyxia uttered, "There is, actually."

"Oh? Please tell me."

"It's simple. You just have to increase your mental capacity, so you never get mentally exhausted," Nyxia answered with a smile on her face.

"..." However, Rudy didn't seem impressed by her response.

"What?"

SIGH!

"That was an obvious answer. You need to tell me a way to increase my mental capacity. I have tried to think of various ways but failed all of them. The only way I can think of is exhausting myself again and again, but now that seems dangerous as I can go berserk. So now, I am left with no option," Rudy asserted with a weary sigh.

Even though he no longer felt exhausted, his face seemed tired as he couldn't comprehend anything. It was out of his knowledge, and he felt stuck for the first time in his life.

So far, his powers and intellect have helped me overcome every challenge he faced, and his knowledge and experience from his past life helped him considerably.

"You need to cultivate it."

"Uhh…. what?"

"Cultivate your mental capacity. If your mental capacity can increase the more you use your powers, then it should also increase if you manually cultivate it instead of resetting," she stated.

"So this 'cultivate' is the same as recharging, am I right?" he asked with a curious and confused look on his face.

Nyxia nodded and continued, "Not entirely, but yes. When you take a rest, your mental strength recharges, but that takes a lot of time, and you need to rest compulsorily. But in cultivation, the recharging speed would be much faster, and the more you cultivate, the more your mental capacity will increase."

She explained in a calm voice.

"You still haven't told me how to do that, though."

"There are different types of cultivation methods depending on what you want to cultivate. Let me ask you, what do you want to cultivate, and how far can you go for it?"

"You already know the answer."

"Are you interested in dual cultivation?" Nyxia asked curiously.

"By the name, I guess it's cultivating two times or something?"

"No. Dual cultivations basically means sex," she said nonchalantly.

"Uhh… then aren't I dual cultivating all the time?" Rudy wondered.

Nyxia shook her head and uttered, "No. To dual cultivate, your partner has to be someone with great powers. Humans are powerless, so obviously, you can't dual cultivate with them."

"What about vampires? Jane and I have fooled around more than you think."

"You can't do that with vampires either. You see, there are many requirements. We, vampires, don't have any spirit in our bodies. If we die, we turn into ashes, and we can't revive them."

'But didn't you try to reincarnate your husband?' Rudy wanted to ask Nyxia, but he knew that doing that in the middle of an important conversation might make her mad, and he would never get another chance to discuss cultivation with Nyxia again.

"Then can I dual cultivate with ghosts?"

"No."

"What about dragons?"

"Only a few who have dragon magic."

"Then who do you think is a compatible partner for me to dual cultivate with?"

"Try elves. You can never go wrong if elves are involved. But unfortunately, you can't find them. They closed all the portals to their world and secluded themselves with the rest of the races."

"Any other race?"

"Fairies should work too, but they are super toxic in nature," she informed.

"That doesn't match the description of the fairies I had. But there are many types of people in the world."

Rudy recalled what the landlord had told him about the fairies, and from that, he assumed that they were naive in nature.

"Are there any other ways?" Rudy asked curiously.

"For what, cultivating or dual cultivating?"

"Hey, what about vitality?"

"What about it?"

"Since you said I sucked your vitality with your blood. Can't I create vitality with my powers or something? Or maybe even cultivating it?"

Nyxia stared at Rudy for a few seconds before replying, "Even I have limited knowledge about it. And believe me, that's not something you should be seeking."

"Why… not?"

"There are things better left unknown. There is a limit to how much knowledge one can hold; expose them to reality, and they go insane. I am saying this for your own sake," she said with a calm yet concerned look on her face.

"I understand. Thanks for telling me about this new way to increase my mental capacity. I will look into it more thoroughly and find a better alternative if needed."

All this time, Rudy was stroking Nyxia's head, and she was still on his lap. Whenever Rudy spoke, he moved his right lap up and down, making Nyxia look like a baby in her father's lap.

After they stopped talking, Nyxia sat up and wrapped her arms around Rudy's neck while still sitting on his lap. She pushed him back on the pillar he was leaning on and looked into his eyes before uttering:

"You never apologized for suddenly attacking me and never rewarded me for giving you a ride."

"I.. was going to do just that."

Nyxia glanced at Rudy's lips before moving her gaze to his neck. She licked her lips and gulped down before asking: "Can I drink your blood?"

"Sure."

Nyxia instantly opened her mouth and buried her fangs in his neck. She sucked his blood for about a minute and pressed her lips on his lips.

"..."

Rudy didn't stop her and kissed her back, and they enjoyed the mixed tastes of each other's blood and saliva.

Thanks, @Robert_Heieck, for the gift!