I do not wish to continue HNG as Fujiwara Sai is gone from the story and I find that hes the main character of HNG.
Isn't Hikaru the main character? Sai's mission is to assist Hikaru until he awakens his talent. Once Sai is no longer needed, he has fullfilled his mission and thus his spirit can rest in peace. It's kinda sad the way it ends but life must go on.