This is a short anime episode, centering around Yumiko Sakaki. The episode consists of Yumiko and Yuuji hiding in a locker in the bath.
When Yumiko and Yuuji encounter each other in the bath, Yumiko hides with him as the other girls come to take a bath, as to not get the wrong impression about the two of them.
Although this is a recollection from Yuuji for JB during a job promtion, it is unknown at exactly what time the events take place.
Although it will later be part of the blu ray DVD release of Grisaia no Rakuen, these special episodes are still being created.