Another fun fact about the "second" (mostly applicable towards execution via seppuku): it was considered both a mark of skill and respectful to the deceased and the audience to cut through just enough of the neck to leave the head hanging by a flap of skin.The translation note is kinda interesting.
Basically, a Samurai performing Seppuku would have a "second", who was in charge of beheading them for a quick death.
Ryouko telling Carol that she would perform the beheading is essentially saying that if Carol was suicidal, she'd end it quickly right there.
TLDR; if you wanna fuck around, don't pull others into it.
True, but it feels like she's cocky given that she found a way they can possibly deal with Mc "I can kill your foot" which makes sense since she's young.I like Carol, she's quite fun. It's nice to see another person who knows about his abilities, but just treats him like another person.