Agate Crosner

Agate is one of the main protagonists of the Legend of Heroes: Trails in the Sky group of JRPG games that pops into Joshua's team at several intervals. This is particularly due to the terrorists making people's lives a living nightmare. And that he owed a great debt of gratitude to Estelle's father.

It was later revealed that he was a former member of the Ravens group, a group of punks that Joshua met early on into the game. Fortunately Estelle's father stopped him.

Now, he works as a bracer. Kind of like a Good Samaritan that tackles big and not so big jobs.

Personality
He comes off as a tough guy, not wanting to admit that he's wrong at times. Sometimes he may send the wrong message when he's within Joshua's team.

Still, this is not to say that he is a bad guy. Even Tita admits that he doesn't know the right words to say in order to convey his feelings to the group.