SWORD ART ONLINE: FATAL BULLET

Dissonance of the Nexus DLC

There are 26 total Emblem Earrings for the set, from A-Z.

The School Uniform costume can be obtained from the Hidden Event quest purchased for 50,000,000 credits from Argo the Informant at her location out in the Urban District in SBC Glocken (she won't sell you information anywhere else).

The quest requires you to collect the 26 Earrings and then talk to the Accessory Exchange receptionist in the back right of the PvP counter in the Lobby in SBC Glocken. The receptionist will be astonished by your Earring collection and give you the school uniform costume set as a gift/reward.

Finally, you will need to head over to Asuna's Outfitters in Kirito's Room and craft the School Uniform F. After that, the achievement should pop!

School Uniform F:
-10 Supreme Cloth (drops from AI players in White Frontier)
-7 Premium Cloth (drops from AI players in Forgotten Woods on Extreme)
-5 Rare Cloth (drops from AI players in Forgotten Woods on Normal)
-10 Organic Bee Antenna (drops from bees in White Frontier, should have a ton by the end of the DLC)

Treasure chests in the Dissonance of the Nexus DLC can be opened more than once if you fast travel and re-load the area. Emblem Earrings are guaranteed from their designated chest, so if you open a chest and don't see it or an Unidentified Item, then you haven't found the correct chest yet.

I actually purchased the Argo info after I had gotten all 26 Earrings, so I'm not sure if the Hidden Event quest provides markers for all of the Treasure Chests throughout the DLC. Therefore I will provide a text list here: (still editing)

Emblem Earring A (White Frontier Chest - on the other side of the ridge from Icicle Prison, under Solo Stinger)

Emblem Earring B (White Frontier Chest - southwest corner, due south of Meteorological Ruins, protected by 2 Arctic Delinquents)

Emblem Earring C (White Frontier Chest - center north, due north of Earring A chest)

Emblem Earring D (White Frontier Chest - northwest corner next to Cursed Rune)

Emblem Earring E (White Frontier Chest - just north of SBC Abend on top of the ridge)

Emblem Earring F (Ruins - First Area Chest)
Emblem Earring G (Ruins - First Area Chest)
Emblem Earring H (Ruins - Midpoint Area Chest) (behind the door requiring Observation 3)
Emblem Earring I (Icicle Palace Chest)
Emblem Earring J (Icicle Palace Chest)
Emblem Earring K (Icicle Palace Depths Chest)
Emblem Earring L (Hero Party Quest 1)
Emblem Earring M (Hero Party Quest 2)
Emblem Earring N(Hero Party Quest 3)
Emblem Earring O (Hero Party Quest 4)
Emblem Earring P (Hero Party Quest 5)
Emblem Earring Q (Hero Party Quest 6)
Emblem Earring R (Hero Party Quest 7)
Emblem Earring S (Hero Party Quest 8)
Emblem Earring T (Hero Party Quest 9)
Emblem Earring U (Hero Party Quest 10)
Emblem Earring V (Hero Party Quest 11)
Emblem Earring W (Hero Party Quest 12)
Emblem Earring X (Hero Party Quest 13)
Emblem Earring Y (Hero Party Quest 14)
Emblem Earring Z (Hero Party Quest 15)

(still editing, I will attach the remaining screenshots soon, they take about a week to upload to TA)