Akeno's oni control

Ura — the famous evil Oni that became the head of its kind and lived in Onigashima in the Momotarou story. Ibaraki Douji — a legendary Onigami[1] who served as the right hand of Shuten Douji, one of the three great Youkai of Japan. Rossweisse then figured out that Akeno had made a contract with these two Onis as her familiars. Akeno said,

“Thanks to the kindness of my cousin, Suzaku-neesama, I was able to enter the Himejima house.There, I asked to — strengthen the power that I inherited from my mum which flows through my blood.”

Akeno controlled the small Oni. Rossweisse had heard about this before. Akeno’s mother was easily liked by Oni. Akeno herself also had a good relationship with a number of small Oni in her childhood. …The Five Principal Clanshad a deep relationship with the monsters and Youkai in this country. She probably succeeded in making contract with the famous Oni through the Himejima household. In this Rating Game, there was a limit to a familiar’s usage. If that weren’t the case, the player wouldn’t need to fight by themselves as they would only need to make a contract with strong monsters and have them fight. For that reason, there was a time limit to summoned beings.

True DxD Volume 2, Middle Game