Akihiko's not perfect. He spends a good deal of his character arc dealing with the stresses of tackling shadows, being all reckless. He's rather closed at first, especially if you're romancing him. Then Shinji appears and you get all the drama surrounding that.

He isn't perfect, he just doesn't have any obvious imperfections like the crazily lecherous Junpei has.

If it sounds like I'm really beating on Junpei, I'm really not. I definitely prefer late-game Junpei to early-game Junpei. He does have good character development (which mainly centres around Chidori, to be honest), but I like that he grows up.