Nanami is Riou's step-sister and was adopted by Genkaku. Growing up, she spent most of her time with Riou and Jowy—basically just the three of them—which made all of them social outcasts. She's known for her deadly skill with the three-piece-rod and her speed in combat, which is hard to match. After Genkaku died, she tried to keep his dojo running, but it didn't work out. That failure pushed Riou to join the military instead.
When Riou came back, both of them got locked up, but Nanami managed to escape and signed on with Viktor's Mercenaries. From that point on, she stayed close to Riou as his protector, though she began questioning things once he took charge of the Unification Army. She wasn't sure why the burden had to fall on him.
She tried convincing Riou to drop everything and run away with her multiple times, but he refused to stop fighting. Eventually she accepted that he wasn't going to quit, but it secretly tore her apart—especially knowing that meant he'd eventually have to face Jowy, their childhood friend, as an enemy. During the siege on Rockaxe, an arrow from Gorudo's Knights hit her hard, and she seemed close to death. But it was deliberate. Exhausted from watching Riou suffer and unwilling to fight Jowy, she faked her death and hid out in Kyaro for the rest of the war. After it ended, she rejoined both Riou and Jowy as they moved forward.
Content compiled by AnimeList.moe from publicly available sources.