"Áo Dài" (literally "long dress") is the national dress of Vietnam, as well as the uniform for Vietnamese high school girls in certain days (like Monday, formal occasions or some holidays).. And yes, it's really form-fitting - the Vietnamese Ministry of Education is truly men of culture..

also, can we please make "ao dai" a tag on ehentai? in the meantime, I will hijack the "schoolgirl uniform" tag..

List of artists and their pixiv
Cover: ぶっくりP : https://www.pixiv.net/en/users/5094596
002-009: Nguyen Tam Lee : https://www.pixiv.net/en/users/7629816 (an artist focus on military girls in Vietnam War)
010-014: phap2000 : https://www.pixiv.net/en/users/38586207
015-023: FuyuDust : https://www.pixiv.net/en/users/39648241 (an artist focus on Vietnam topics in general)
024: Shisarou : https://www.pixiv.net/en/users/13506288
025: Acul_chan : https://www.pixiv.net/en/users/19995034
026-028: 悲しみ : https://www.pixiv.net/en/users/5148157
029: snonfield : https://www.pixiv.net/en/users/13952994
030: beNai0204 : https://www.pixiv.net/en/users/12207726
031: Xion : https://www.pixiv.net/en/users/3850071 (an artist focus on yuri and selfcest)
032-045: Hiep Studio : https://www.pixiv.net/en/users/30780986
046: 柴生かなた : https://www.pixiv.net/en/users/1452672
047: FluffyQueenz : https://www.pixiv.net/en/users/15626765
048-049: ぴちぴちデニムまつり : https://www.pixiv.net/en/users/16153560
050-053: siriuflong : https://www.pixiv.net/en/users/6414018
054-055: nannacy7 : https://www.pixiv.net/en/users/57085
056: raffijoe5 : https://www.pixiv.net/en/users/20584918
057: LVoxx : https://www.pixiv.net/en/users/30464200
058: Higeneko : https://www.pixiv.net/en/users/11396747
059-060: ba_mi : https://www.pixiv.net/en/users/38353968
061-064: なんじゃ : https://www.pixiv.net/en/users/8885157
065-066: Keaton : https://www.pixiv.net/en/users/856758
067-068: ミツキチカノ : https://www.pixiv.net/en/artworks/84043876
069: 葉月 光 : https://www.pixiv.net/en/users/11833485

Update 27/11/20
070: VonTornado : https://www.pixiv.net/en/users/28593902
071: Bainbridge : https://www.pixiv.net/en/users/321941
072-075: ばか☆黒龍 : https://www.pixiv.net/en/users/18047636
076: Ginn : https://www.pixiv.net/en/users/36947879
077: 6x2 : https://www.pixiv.net/en/users/22649431
078-079: 日暮 七十七 : https://www.pixiv.net/en/users/2283371
080: ひでつろ®️ : https://www.pixiv.net/en/users/37046432
081: sheepD : https://www.pixiv.net/en/users/14807885
082: うおぬまゆう : https://www.pixiv.net/en/users/25719
083: Coffee Bean : https://www.pixiv.net/en/users/21645058
084: 雪抹茶 : https://www.pixiv.net/en/users/14999392
085-086: とんなぐ : https://www.pixiv.net/en/users/258901
087-089: Yuriniel - 晃湧 : https://www.pixiv.net/en/users/18813645
090: きずみ : https://www.pixiv.net/en/users/34300616
091: 校長 : https://www.pixiv.net/en/users/10033894
092: あきのこと : https://www.pixiv.net/en/users/2666367
093: ねうる : https://www.pixiv.net/en/users/5774481
094: CCoordinator : https://www.pixiv.net/en/users/39505733
095: ITサラリマン : https://www.pixiv.net/en/users/45720982
096: 瓜硝子 : https://www.pixiv.net/en/users/3428600
097-098: koba（ももれぷ : https://www.pixiv.net/en/users/8033672
099: コボリヤスヒラ : https://www.pixiv.net/en/users/20463915
100: dishwasher1910 : https://www.pixiv.net/en/users/13408193
101: Kittona : https://www.pixiv.net/en/users/1537530
102-103: urute : https://www.pixiv.net/en/users/3622
104: はとば佑 : https://www.pixiv.net/en/users/43744004
105: 御子神 : https://www.pixiv.net/en/users/5583577
106: 白水 : https://www.pixiv.net/en/users/43595048
107: なぶ : https://www.pixiv.net/en/users/276199
108: Larribee : https://www.pixiv.net/en/users/4160602
109-126 : わーうるふ03 : https://www.pixiv.net/en/users/13014433
127: FED : https://www.pixiv.net/en/users/284551
128: Cy. : https://www.pixiv.net/en/users/32791
129-130: Toba Yuga [跳馬遊鹿] : https://www.pixiv.net/en/users/1254236 - gallery HERE

Update 25/12/20
131-132: はるまき（晴永牧兎）[Harunaga Makito] : https://www.pixiv.net/en/users/69998
133: 欠 : https://www.pixiv.net/en/users/9139792
134-136: あしはら : https://www.pixiv.net/en/users/1511734
137: 猫月ユキ : https://www.pixiv.net/en/users/2077206
138: Rima : https://www.pixiv.net/en/users/42814117
139: 葛切 : https://www.pixiv.net/en/users/13039060
140: ヨンシキ : https://www.pixiv.net/en/users/19562765
141: カンパ : https://www.pixiv.net/en/users/2520952
142: 化猫丸 : https://www.pixiv.net/en/users/33519968
143: ぽち子 : https://www.pixiv.net/en/users/21546177
144-147: アークナイトⅡ : https://www.pixiv.net/en/users/2485595
148: 葵ざよう（aoizayou）: https://www.pixiv.net/en/users/21085826
149: 綾智 : https://www.pixiv.net/en/users/14252538
150-151: mousanex : https://www.pixiv.net/en/users/5242700
152: 童 : https://www.pixiv.net/en/users/386861
153: FrequencyBlue : https://www.pixiv.net/en/users/3997910
154: ORGEL : https://www.pixiv.net/en/users/197139
155: ところによりはれ : https://www.pixiv.net/en/users/4063556
156: kodue : https://www.pixiv.net/en/users/220539
157: はらしゅう : https://www.pixiv.net/en/users/459334
158: すえゆう : https://www.pixiv.net/en/users/1525543
159: 宮瀬ぬっこ : https://www.pixiv.net/en/users/5094870
160: 緋仙カエデ : https://www.pixiv.net/en/users/2053497
161: モンスーン : https://www.pixiv.net/en/users/3449626
162-164: 一条高雪 : https://www.pixiv.net/en/users/13173
165: 棕毛 : https://www.pixiv.net/en/users/7383361
166-169: ヤオ : https://www.pixiv.net/en/users/88227
170: モロコシ : https://www.pixiv.net/en/users/4752647
171: 江久井 : https://www.pixiv.net/en/users/19904161
172: kaja344 : https://www.pixiv.net/en/users/16649361
173: nu64 : https://www.pixiv.net/en/artworks/70576460
174: 吉川すずめ : https://www.pixiv.net/en/users/5465316 (furry artist)
175: 御崎悠 : https://www.pixiv.net/en/users/8872168
176: オウカ : https://www.pixiv.net/en/users/4552399
177: 霜月つらら : https://www.pixiv.net/en/users/15694806
178: シャコバ : https://www.pixiv.net/en/users/22804928
179: ひでぇ : https://www.pixiv.net/en/users/4098877
180: NOLIA : https://www.pixiv.net/en/users/4962782
181: テケえもん : https://www.pixiv.net/en/users/553166
182: 乙夏 : https://www.pixiv.net/en/users/212425
183: k_saky : https://www.pixiv.net/en/users/18632463
184: らび : https://www.pixiv.net/en/users/1100743
185-186: Haya. : https://www.pixiv.net/en/users/4712684
187: ぽっちー : https://www.pixiv.net/en/users/10295403
188: irua : https://www.pixiv.net/en/artworks/59625950
189: 我が名は見習いあんのうん : https://www.pixiv.net/en/users/20185
190: 土 : https://www.pixiv.net/en/users/677112
191: らぐほのえりか : https://www.pixiv.net/en/users/101500
192-197: Mirunai : https://www.pixiv.net/en/users/455890
198-199: The-Sinner : https://www.pixiv.net/en/users/895393
200: いっしたいら : https://www.pixiv.net/en/users/16535
201: 前山 三都里 : https://www.pixiv.net/en/users/86033
202: genya : https://www.pixiv.net/en/users/2066594
203: nhan0121 : https://www.pixiv.net/en/users/3787934
204: AT2. : https://www.pixiv.net/en/users/330401
205: Pansy : https://www.pixiv.net/en/users/15478026
206: Lost : https://www.pixiv.net/en/users/5882637
207: かおるちゃん : https://www.pixiv.net/en/users/2061245
208: うにゃうさちゃん : https://www.pixiv.net/en/users/494083
209-213: 大型犬 : https://www.pixiv.net/en/users/413491
214: モグぽん : https://www.pixiv.net/en/users/13820247
215: 背川 昇 : https://www.pixiv.net/en/users/2969152
216: akira : https://www.pixiv.net/en/users/1034271
217: シェリラ : https://www.pixiv.net/en/users/4668761
218: cyan : https://www.pixiv.net/en/users/41107
219: GarukuC96日西N08a : https://www.pixiv.net/en/users/792198
220: 茶菓子 : https://www.pixiv.net/en/users/177582
221: sat（ゆきぽ派） : https://www.pixiv.net/en/users/815222
222-239: 矢木坂せと : https://www.pixiv.net/en/users/3557
240: 春夏冬工 : https://www.pixiv.net/en/users/5691
241: ラム茶 : https://www.pixiv.net/en/users/2665510
242: fantomdelucifer : https://www.pixiv.net/en/users/1110344
243: たまつー : https://www.pixiv.net/en/users/29514
244: オペラ : https://www.pixiv.net/en/users/3408043
245-246: 草凪蜻蛉 : https://www.pixiv.net/en/users/967117
247: 辻風 : https://www.pixiv.net/en/users/252845
248: 唯月 : https://www.pixiv.net/en/users/302416
249-250: nix : https://www.pixiv.net/en/users/3395027
251: おもちまる : https://www.pixiv.net/en/users/411078
252-253: 夏樹 : https://www.pixiv.net/en/users/4969
254: i.u.y : https://www.pixiv.net/en/users/520159
255: 有希 ひつぎ : https://www.pixiv.net/en/users/709552
256: びりー : https://www.pixiv.net/en/users/427342
257: kusakabe : https://www.pixiv.net/en/users/5378
258: かざあな : https://www.pixiv.net/en/users/65404
259-260: すぽぽ : https://www.pixiv.net/en/users/295235
261: 大江山健 : https://www.pixiv.net/en/users/23909119
262: あすとら : https://www.pixiv.net/en/users/1238467