Persona 5 Royal
52 Achievements
1,000
100-120h
Professional Modification
Customized a gun.
15
14.0%
How to unlock the Professional Modification achievement in Persona 5 Royal - Definitive Guide
To do so, try the Big Bang challenge in Shibuya until you get where you want to.
Then, visit Iwai at the Airsoft Shop and tell him you want to talk about the bag.
That will begin his Confidant line which is the Hanged Man.
On his very first rank you will be able to modify ranged weapons to either improve their accuracy or their damage for a small fee.
This also unlocks the achievement.
*MISSABLE*
In the military store in Shibuya, you can customize guns for use in dungeons. This trophy involves customizing a gun for the first time. Gun customization requires a Confidant Rank 1 with Munehisa Iwai, the owner of the gun shop. This in turn requires your social stat Guts to be rank 4, so it'll be fairly late into the game before you can do this.
Once you have Guts at rank 4, speak to Munehisa Iwai in the gun shop to start his Confidant and reach rank 1. As this spends time, return the next day and speak to him again to access his shop. You can customize guns you already own or any gun that you purchase from Iwai.
If you have a gun you want to customize, navigate to the last option of his menu. Here, you can pick one of your guns. Pick any upgrade to customize the gun with. If you want to customize a new gun instead, you can purchase any gun from Iwai, and you will be asked if you want to customize it right away once you buy it. When you enter the customization menu, you'll have several options to pick from. Each increases accuracy, power or other stats, so pick the ones that suit your playstyle the best:
In either case, the trophy will unlock as soon as you customize a gun for the first time.