Crane Style - Unarmed Only?

[MajorTotoro]

So, a player of my Serpent Skull's Campaign wants to take this feat tree. He plans to use it with weapons, but it seems to me that it's meant to be used only with Unarmed strikes. It's not specifically stated, but it is mentioned in the flavour text, and it does require Improved Unarmed Strike. What do you think?

[Maxximilius]

You need at least a free hand to use the higher feats, but the first one (Crane Style) doesn't require to be unarmed, only to be proficient in unarmed combat.

[Interzone]

Yeah, you need a free hand, but the AoO for crane riposte does not have to be unarmed.