Persona 5 Tactica

For this achievement, after you make your first return to LeBlanc with Erina now on your team after fleeing Lady Marie, she'll bring up the need for you to stock up on the best up to date weapons. To access the weapons shop, select Hideout, then scroll to the bottom to select Shop, and then select your character to get a list of guns available. At the start, you'll have two different weapons available for each character, one that is slightly more expensive but also does more damage, and the other is cheaper at the expense of weapon power, but you get longer range in return. You can purchase both as long as you have enough money (which you can earn from replaying and finishing previously completed missions by selecting Hideout > Replay to find the list of missions). The earliest you can buy the 10 weapons needed to unlock this achievement in terms of main story progression will come after you rescue Ryuji and Haru (completing Mission 11), and from there you can buy for those two to go along with Joker, Erina, Morgana, and Ann.