There's an unorthodox minor/adult relationship. It's not the standard type of disturbing of, say, a 30 yr old 'dating' a 16 yr old. It's a similar theme that comes up in certain anime at times, if you're familiar with those. It wasn't enough to make me stop reading but I was definitely uncomfortable with it and kept thinking about it throughout the reading.

So there was a 16 year old and a hundreds of years old immortal being that's in a teenaged body. This felt icky to me bc even though they did present and interact with the minor as a fellow teenager, they had the literal mind of a multi century old adult. They even mentioned them dating a present character's dead grandparent in the past. It's just weird.