Power and its responsibilities is also a big theme. As the characters gain more power, they have to learn how to use it properly and not let it corrupt them. It's a constant struggle and a major part of their growth throughout the novel.
Issei Hyodo is one of the main characters. He is a perverted high school student who gets involved in the supernatural world of devils. Rias Gremory is also important. She is a devil and a powerful character in the story.
One of the main themes is the supernatural elements. It involves devils, angels, and other mythical beings which create a complex and exciting world. Another theme could be the growth of the main character. He faces various challenges that force him to become stronger and more mature.
One interesting storyline is the growth of the main character in his power and relationships. He constantly faces challenges and overcomes them, forging stronger bonds with his friends and allies along the way.
The content of the 13th volume of the novel " Demon High DxD " was as follows:
In the third chapter," The Lost Glory," the protagonist, Armstrong, and his companions came to a mysterious ruin and found the legendary Demon Sword.
This sword has a powerful force that can give the wielder a powerful ability. However, this sword also had a dangerous weakness. Once it was attacked, the wielder's body would fall into a deep sleep and wait for the next awakening.
In order to obtain the Devil's Sword, Armstrong and his companions engaged in a fierce battle. In this battle, not only did they have to face powerful demons, but they also had to face their own fears and uneasiness.
In the end, Armstrong and his companions defeated the Devil's Sword, but they also realized that this battle would not end so easily. They needed to continue fighting until they achieved true victory.
In the fourth chapter," The Power of Darkness," Armstrong and his companions began to explore the depths of the ruins and found a mysterious cave. In this cave, they found a huge demon waiting for them.
In the end, Armstrong and his companions engaged in a fierce battle with the demons. In this battle, not only did they have to face the powerful strength of the demons, but they also had to face their own fears and uneasiness.
Through this battle, Armstrong and his companions became stronger and understood themselves better. They decided to continue exploring the ruins in search of more treasures and secrets until they achieved true victory.
We can expect more exciting adventures of the characters. There might be new power-ups, more intense battles, and deeper exploration of the relationships between the characters.
I don't think it's a good idea for a newcomer to start with Volume 23. It's better to start from the beginning to understand the characters, the world - building, and the basic plotlines.
I'm not sure specifically as I haven't read Volume 23 yet. But generally, in the High School DxD series, we can expect more development of the characters, new supernatural elements, and exciting battles between different factions.