Part 10 and Side-Story 16 are done. After getting this far, I felt bad for Chi-chan. Anyway, there's still Part 11, I'll be taking my break again.
Looks more like Ri-class (plus pixiv tag and in-story text seems to agree). And I felt bad for her too (esp. since from her point of view, her sister was murdered in cold blood).
It's especially tragic because this was completely meaningless. Not Ri-Class' actions, but the Admiral's.
When you're fighting for humanity's survival against an enemy you barely know anything about, you don't execute an injured enemy soldier you luckily stumbled upon; you capture them for interrogation!
It's even stupider on his part because she was missing a leg, and he outright stated he knew that meant there was one more, yet instead of using Ta-Class as a hostage to capture the Ri-Class, he finished her off and then practically sat outside waiting for Ri-Class to show up (instead of setting up an ambush in the cave).
Then he let Ri-Class run away, despite knowing that she would eventually become their enemy again. Any innocent people, fellow naval men, or shipgirls killed by that Ri-Class are now partly on his head!
The Macho Admiral is a great guy, but this was a classic example of honor before reason.