Is this a spoiler for someone who wants to read the manga?

Hi!!! I watched this masterpiece a few weeks ago and recommended it to a friend. He liked it so much that he's going to start reading the manga. Personally, I usually don't mind getting spoiled about certain details since I never read the manga myself, so I actively looked up information and found out that the Hiruko were actually members of the academy (I was blown away)

The thing is, my friend hasn't noticed that yet (only about Mimihime and Shiro), and I'd love for him to realize it so I can see his reaction. That's why I’d like to know if this is explicitly stated in the manga, or if it’s something you're supposed to "figure out", and whether telling him would ruin the experience

Thanks so much for the help and for taking the time to read this, have a great day!