Yakuza: Like a Dragon

Joon-gi Han joins your party at the start of Chapter 10. There isn't anything holding him back from max bond level right away. You get 5 bond xp for each battle or a faster method is to buy food at a restaurant. I went to Bar Rodriguez outside of the Survive Bar and bought the cheapest thing for $400. Each time you buy it you get 10 bond xp. Just do this until you no longer get xp and run to the Survive Bar to have the talk that unlocks the next rank. I had to eat about 17 times to get from rank 4 to rank 5 which is $6800. That's not a lot of money at that point in the game. At the end of rank 4 you will have a fight like with the other party members. It's pretty easy.

This method works for all party members, but Nanba will not go past rank 2 until chapter 10.