Yakuza 5 Remastered

Partway into Part 1, Chapter 3, an exclamation point will appear on your map north of Kiryu's apartment. There, you'll find someone that’s being accosted. Go to the exclamation point and Kiryu will recognize him as Kamiyama. Kamiyama has been in prior games as someone who can craft weapons and armor for you. Kamiyama has a shop in every city. The only character who can’t use the shop is Haruka since there’s no need for her to use it.

How it works: While K-Works has some weapons and armor available for purchase immediately, the rest of the equipment comes after you invest in his shop. There are two ways to invest, money or items. Investing items (wouldn't recommend leveling this way), but there are some crafting items like the mystery stone that you're required to invest to unlock specific new weapons and armor if you're going for the 100% completion. If you just want the achievement you can invest with money to get further towards the Level you want.
Here are the requirements for each level:
Level 2: 5,000 yen
Level 3: 10,000 yen
Level 4: 15,000 yen
Level 5: 20,000 yen
Level 6: 30,000 yen
Level 7: 50,000 yen
Level 8: 100,000 yen
Level 9: 120,000 yen
Level 10: 150,000 yen