Shingeki no Kyojin: Lost Girls
進撃の巨人 LOST GIRLS
LOST GIRLS tells of the times and spaces in between the plot points, through the eyes and ears of the saga's toughest - but more taciturn - heroines. What they thought, and felt, and did on and off stage come to the fore via a medium distinctly suited to conveying interiority: language.
(Source: attackontitan.wikia.com via AniDB)