Everyone who has reached this page has already watched the main anime certainly. This extra part are short scenes shown after episodes 1-4,9 and 12. Everyone wished that the main anime was longer than just 12 episodes for sure. The short scenes here are only a small consolation but still enjoyable.
STORY:
After the relevant episode, we get a little deeper insight into certain situations afterwards. They are not story-relevant scenes, but we still get to see one or two more small details.
CHARACTER:
The characters act the same as in the main part. They behave in the same way here and act with each other. The most important point is, we learn a little more about them.
ART:
Here we get to see every small detail as well. Even those little things were presented precisely. You can feel the atmosphere of the treated episode well.
SOUND:
Although there is no music, the sound noises also fit here. You can hear small noises in the background, the conversations are presented well.
ENJOYMENT:
Learning one or the other new thing about the characters is certainly exciting. That is what makes these little scenes special. Even if it has no effect on the main part, you certainly want to see and experience as much as possible.
My recommendation is to watch the extra part immediately after the respective episode in order not to miss any detail. It would certainly be nicer if we had more full episodes instead of this, but we can see and enjoy that as a little bonus.