I'm surprised no one's mentioned this yet, but that's a low-key confession, isn't it? I mean, Koguma-chan has clearly been slowly recognizing her feelings, and been growing more comfortable with Hino-san despite all her embarrassed protests. For all that Hino-san is enjoying teasing her and putting her in perverted and embarrassing situations, she's been keeping Koguma-chan at arms length whenever things get serious.
Here, Koguma-chan refuses to be kept at arms lengthin a serious moment, and instead forces herself into a compromising position with Hino-san deliberately, basically declaring that she's not joking around anymore. I so can't wait to see what happens after this.