To be completely honest its something that you have to read more than just once or you wont understand why this manga is good. First and for most *SPOILERS* the girl dies but not really... for the boy she is dead but in the real world she is alive, its extremely complicated tbh i think the author is a genius ngl the ART was FXCKING AMAZING."shounen shoujo" means "little boy and little girl" dont get it confused with the genre its nothing like shounen AND DEFINITELY NOTHING LIKE SHOUJO. Another thing i should say is that it is and absolote mind fxck of a read thats why read it thoroughly and make sure you trully understand the words.
to be completely honest i dont thing anyone will understand this unless you read it more than once