Forbidden Boy Plus A

A story about a child make friend with a wrong person and die in the end...

Nagisa had make friend with another child who's older than him...
Although they may look alike but there's some differences between them like they both have same length hair but Nagisa's is blue while the child's black,Nagisa has big blue eyes while the child's eyes are small and red in colour

When Nagisa is 14 years old,everything changed...
Betrayal,the way to death,nightmares and more...

What will happened to both of them in the end?