Need some help creating an FE character idea for a ROM.

[BlackSymphony]

So I decided that I'd try to create a character in a FE ROMhack that would have a relation with the protagonist.

The person in question is a really young boy who happens to be a wyvern rider. The person was raised from birth to be a vicious warrior for a secret guild taking orders from an antagonistic force. Think it as an Assassin's guild, except without any subtlety.

Now, the character is young, and really has a childish mentality, thinking of his job of terrorizing targets then killing them a 'game' of sorts. This person was not allowed to have any true friends, only people seen as allies to take people down. He was first met by the protagonist, and quickly grew attached to him for his kindness and help, although he tried his best to look up to the protagonist as a 'master'. After being told by a group member that he had an important target, say, a person the protagonist is trying to meet, he runs away from the protagonist after leaving the castle/meeting area/sanctum/whatever, and comes back with a whole group of killers raiding the place to take the target's life, alongside a boss who told him to raid it. He can be talked out of it, but he will just simply not attack anybody else for the rest of the chapter, and will question whenever or not he is in the right.

A few chapter's later, I decided he'd be confronted by his superior, who takes the protagonist by surprise, alone. After being ordered to kill the protagonist, the wyvern rider refuses, and after being attacked by the superior for disobeying orders, he brutally kills him just to show the protagonist he treasures the friendship he had with him, even more than his duty to the group.

So, how shall I play this out?