It's possible that there is a new love interest introduced in Volume 9. This character could be someone who is quite different from the protagonist's previous relationships. Their relationship could develop in a way that tests the protagonist's maturity and understanding of love, while also adding a new layer of complexity to the story's overall narrative.
I'm not entirely sure which new characters are introduced in Volume 12 specifically. But it's common in the series for new characters to be related to the main character's new adventures or challenges. They could be fellow students if he's at a new school, or locals from a new place he visits.
There may be a new teacher figure who plays a crucial role in the protagonist's magical training. This character could bring in new techniques and knowledge.
There might be a new mentor - like figure who has a unique perspective on magic. Maybe there's also a new rival, someone who challenges the main character in his pursuit of knowledge or power. These new characters would add more depth and variety to the story.
I'm not sure which new characters are introduced in this volume specifically. It could be characters related to the new areas or story arcs that start in this volume.
I'm not entirely sure as I haven't read Volume 8 in detail yet, but there could be some characters related to the new places Rudeus visits. Maybe a new mentor figure for his magic studies.
Hard to say. It could be on hiatus, but without concrete information, it's difficult to give a definite answer. Try following the mangaka's social media or the manga's official website for the latest.