lacuna
/ləˈkjuːnə/
noun
noun: lacuna; plural noun: lacunae; plural noun: lacunas
1.
an unfilled space; a gap.
"the journal has filled a lacuna in Middle Eastern studies"
a missing portion in a book or manuscript.
This story is about the 2 Characters Kaeya and Albedo!
They are both guys and this book may have a smut, I'll put a warning though so you don't have to worry!