Yakuza 5 lets you play as series' protagonist Kazuma Kiryu's adopted daughter Haruka, but you won't be able to fight as her.
Haruka won't battle street thugs, series producer Toshihiro Nagoshi told Japanese gaming magazine Dengeki PlayStation (via Andriasang). She will have a different sort of battle element, though it's unclear exactly what that will be. Presumably it will tie into her new role as a pop-star in training.
Also, Haruka can't access some of the game's more adult venues, such as hostess clubs, but she can partake in certain activities closed off to the other characters.
Nagoshi also mentioned the game has twice the volume of Yakuza 4.
Yakuza 5 is roughly 70 per cent complete and due out in Japan this December exclusively on PlayStation 3. A western release has not yet been announced, but if it's anything like the rest of the series, expect it about a year later.