post #4583663 is another official artwork showing Shinobu with her hair down.
It's easier to tell with that post that it's Shinobu. For the depiction above, the bangs need to be swept a little more, and the hair on the sides and back need to wavier, plus her eyes are usually closer to half-closed. As it is, she looks closer to Mika.
Where
did I
drop my
hair
tie...?Ah~!?After this,
Takebe-san came by and settled things down.Anticipated Newcomer※Kawanishi ShinobuA freshman?
Then that means?
You came to check out the Volleyball Club!?You are more than welcome!!Eh?
Um...
that's?When you join the Volleyball Club, you get to ride in a tank!Tanks are fun you know!What'll I do...?
It's getting harder and harder to reveal myself...
