"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