Here is the full list of all 100 Busty Hentai Mosaic achievements.
Outerwear
Koemi, 19
Without underwear, <3
Undressed!
Without a bra
Without outerwear
Emi, 20
Akem, 21
Maeko, 20
Utano, 22
Tsubasa, 21
Shiniqua, 19
Nishi, 22
Hisoka, 23
Kana, 19
Mikasa, 20
Rin, 22
Sugi, 24
Tora, 19
Katsuki, 20
This is B
This is U
This is S
This is T
This is Y
Without Outerwear
<3