I forgot to upload it.

Since the artist has uploaded the whole doujin, he also added this epilogue thing which wasn't here on my digital copy.

I've asked OMGkillitwithfire if it's something important, and it seems it does (be my guest to translate it entirely of course). Here's a sum up he made :

OMGkillitwithfire said:

Destroyer Shigure, one of the highest leveled shipgirls in my naval base.
She disappeared, and later then so did the other 5 shipgirls who have participated the operation.

Even until now, I still find it hard to believe...

Within the few months after that day, one shipgirl who has miraculously averted from sinking told me, "I saw a black shadow, and I heard a faint voice saying 'it is not the time for you to sink yet.'" The aforementioned shipgirl have met Shigure for quite several times, and according to her, that voice is unmistakably "hers". From then on, I have received several similar reports regarding a certain black shadow.

Meanwhile, I was reported that the abyssal forces, who have always been multiplying up until now, have shown signs of depletion. We could not pinpoint the cause. One thing is for sure though, the tide of battle is definitely in our favor.

Speaking of which, it seems that when shipgirls sink (die), their mind and bodies undergo change, and they turn into abyssals. Even until now, there are still shipgirls who have been sunk during battle. Even so, it still doesn't change the fact that the abyssal forces are deteriorating... No, I can't just link all these together with the "black shadow" that easily.

Still, if my assumption is correctly... No, that's implausible.

In any case, this could be a special case in itself, however if "she" isn't an abyssal but some other existence, she might be born out of vengeance and hatred.