Well, a battleship is way heavier than a destroyer or à light cruiser.

... How the hell are you supposed to pronounce "ON HON HON HON HON"? And why is Richileu telling herself to not laugh while in the middle of laughing?

MarqFJA87 said:

... How the hell are you supposed to pronounce "ON HON HON HON HON"?

Something like this.

And why is Richileu telling herself to not laugh while in the middle of laughing?

Mistranslation. Fixed now.

This floor seems surprisingly clean (Yeah, I know, not the original creator of the setting, but still)

The text over the counters are Will (as in, last request letters). The red one is 遺品 (memento).

Kind of bringing a feeling they're already guaranteed certain death in that building.
From the words, Gachi-Oji is talking about his friend's letters he sent out.

I like that, even in the face of Kyouko's bold exclamation that she'll plant the field, Shizuha has the sense to ask "Have you ever done this before?"