She's obviously showing off her ass. Q.E.D. (quod erat demonstrandum, "thus it has been demonstrated," used for mathematical proofs and philosophical arguments)

But wait a minute

Then how do you explain the long coat at the Kure event?

Here, the poster looked at what she was carrying.

First, her right hand... This booklet may be a venue map (foreshadowing).

The problem is the bag in her left hand.

It's huge

She was probably holding on to something for the commander or another shipgirl, but...

What would happen if you walked around like that with such a large bag? I wonder...

Moving around while carrying heavy weights will cause your body to heat up... Because it uses "calories"

Indeed, by the time you arrive the "coat" is no longer needed and can be taken off.

Then under the guise of "guiding you through the venue" she will walk in front,

And show off the ass that she is so proud of!