Reincarnation in DxD with wishes

Grayfia has quite a bit of experience with the power of destruction, due to experiencing many battles, and she lives with Sirzech so she has a lot of experience. It's not for nothing that she is referred to as the most powerful queen in the underworld; thanks to her, I can control the power of destruction more easily.

As you know, the power of destruction has a chaotic nature, so it's difficult to control, but for someone like me, who is an expert at energy manipulation, it's child's play once you get used to it.

While Grayfia continues to train us, I see Rias beside me struggling. 

Theo: "Hey, little sister, you seem to be struggling. Do you need help from your big brother?"

Rias: "Please leave me alone, Theo."

Theo: "Come on, let me help you, just say the word. By the way, you look so cute when you're angry."

Rias: "Theo, Grayfia-sensei, please help, Theo is teasing me."

Grayfia: "Young master, don't tease Rias like that."

Theo: "Grayfia-sensei, you can call me Theo whenever you want, we talked about this."

Grayfia: "Don't change the subject, let's get back to training, both of you."

Theo and Rias: "Yes, sensei."

Grayfia: "Oh, what am I going to do with you two?"

After mastering the power of destruction, I try to focus on the manipulation of shadows and illusions.

And our days go by like this, with training.

Two months later, Rias starts to struggle to keep up with the training. I, on the other hand, have made significant progress in the manipulation power of destructions and shadows. 

During this time, Rias begins to resist training more and more, sometimes not showing up for sessions at all. But I assured Grayfia that I would convince Rias.

I knock on Rias's door.

Theo: "Rias, are you in there? Come on, open the door."

Rias: "I don't want to train, I want to play with you, but we always train."

I enter and sit beside Rias, looking into her eyes. She turns her head away.

Theo: "Look at me, Rias, don't turn your head."

Rias turns her head towards me, her eyes teary.

Theo: "Listen to me, Rias, Mom and Dad want you to be strong to protect yourself."

Rias: "But you're here, big brother, and Sirzech-ni-san too."

Theo: "What if something happens to me? What if I can't protect you? Would you like to see me fail to protect you and die?"

Rias: "No, I won't allow that, let go, Ni-san."

{Trying to manipulate a little kid makes me feel like a scumbag, but if I don't do this, she'll turn into a useless mess like in the future. I understand that forcing someone into an unwanted marriage for political reasons, even if it's your little sister, is wrong, but if Rias had trained herself, she could have resisted it.}

Theo: "I'm not going anywhere, Rias, I'll protect you."

I pull her cheek, and she blushes.

Rias: "Stop it, Ni-san."

Then she pushes me out of the room. Well, I can say our relationship has improved.

Anyway, after being kicked out of the room, I meet my mother.

Venelena: "Why do I occasionally find you here in front of Rias's room, Theo-kun?"

Theo: "Mom, please stop teasing me, Rias is my sister."

Venelena: "The incest within the family is quite high among devils."

Theo: "Stop it, Oka-san."

Venelena: "Alright, do you want to come to the garden with me or are you going to leave me alone?"

Theo: "I'll come with you, Mom."

After going outside with my mother, she brings up the topic.

Venelena: "Theo-kun, you're quite strong for your age, are you? I watched you while you duel with Grayfia, you've grown so much."

Theo: "Mom, I've been training since I was 5, I've had an inhumane training. Being strong is natural for me."

Venelena: "I know, but back then, you hurt me a lot by not spending time with me."

Theo: "I'm sorry, oka-san, I'll spend more time with you from now on."

After that, I went to bed and ignored the fact that I had neglected my family a lot. Maybe initially, I didn't see them as my family exactly; after all, I had trust issues, but I'm starting to fix that now. Maybe it'll disappear eventually, and that night, I slept very peacefully after letting go of what was inside me.