The final stage of the hero's journey. Features the refusal to return, the magical flight, the rescue from without, the return threshold, master of two worlds, sharing the knowledge, and freedom to live.
Return
The refusal to return is the opposite of the one of the first steps, the refusal to the call - in Kazuma's case is is willing to go back into battle to get what he has too. This is proven in 4 when he heads to Kamurocho to sort out the problems that have washed up (literally) on his front yard. Knowing that his retirement as 4th Chairman has caused a lot of problems, he heads back to Kamurocho to talk to Daigo and offer his assistance to Lily who is looking for her brother.
The magical flight is usually a flight from the journey back into the natural world. Usually this also encompasses the rescue from without in which the hero needs assistance returning to the normal world. Kazuma's normal world would be returning to Sunshine Orphanage to be with this children. However, Yakuza 4 leaves that ambiguous. We know he sorts out the Tojo clan strife but, we do not know what happens to the Orphanage. We also know that Haruka is waiting for him outside of Tojo Headquarters for Saejima's induction ceremony. This is a little sketchy in Kazuma's place as we are uncertain of what happens to him and the children. But we assume that he is free to live as he chooses.
The return threshold is the last step the hero must take to return to the natural world. For Kazuma it means sorting out the battles and the yen issues with the Tojo clan. As far as we know everything has been sorted out with Majima and Daigo both waiting on Saejima. It can be assumed that Kazuma is once again an active art of Tojo clan. With Haruka at his side, he will probably want to give her a nice and quiet life. This puts him, more or less, right back where he started - part of the family although somewhat unwilling.
Kazuma becomes the master of two worlds by protecting Haruka and saving the Tojo Clan. He is able to move freely between the two. Doing what he needs to for Tojo clan while looking after Haruka.
The last two steps of the journey are sharing the knowledge and the freedom to live. In Kazuma's case the knowledge he has to share and come to realize is that his quick succession and retirement as Fourth Chairmen sent Tojo clan into an awkward and downward spiral. He apologizes to Daigo for hte trouble he has caused before they battle. With Kazuma victorious he is able to assist in stopping Munakata. In this way he returns peace back to Tojo clan and is then free to live as he chooses.
Because there is a Yakuza 5, some things may change. For instance, we may learn what happened to the Orphanage and if Kazuma gets to live a normal life. I assume, however, that for now he is part of Tojo clan and that Nakahara is looking after the Orphanage. I believe that Kazuma realized it would be easier to stick around and watch Tojo Clan for a while. But I doubt that he would stay forever as he seems to want nothing more than a quiet life.