Perhaps 'Nana' would be of interest. It shares themes of friendship and love, and the art style is somewhat comparable to Black Bird.
You might want to check out 'Fruits Basket'. Both have elements of romance and drama, and the character development is engaging in a similar way to Black Bird.
Some manga similar to Black Bird could be 'Vampire Knight' or 'Inuyasha'. They share elements of fantasy and romance.
I think 'Natsume's Book of Friends' could be similar. It has elements of supernatural and emotional depth like Black Bird.
You might like 'Vampire Knight'. It has a similar supernatural theme and complex character relationships as Black Bird.
The plot could be a key factor. Maybe a similar theme of romance or supernatural elements.
I'd recommend 'Ouran High School Host Club'. It shares elements of comedy and drama with Black Bird and has engaging characters and storylines.
One manga similar to Black Bird could be 'Vampire Knight'. It has elements of romance and supernatural like Black Bird.
Maybe 'Diabolik Lovers' could be comparable. Both have a dark and mysterious tone, and the characters have complex relationships. However, the art styles differ slightly.
Some mangas similar to Black Bird could be Vampire Knight or Chibi Vampire. They share elements of supernatural romance and drama.
The main similarity might be in the style of art or the theme. But differences could lie in the character development or the plot progression.
The story of Black Bird involves a lot of elements like romance, fantasy, and drama. The main character has to deal with various challenges and relationships while uncovering secrets of the supernatural realm.