I'm not sure specifically what 'Cap deage' means. It could be a very specific term, a misspelling, or something relatively unknown. It might be a proper name, a local term in a certain area or a very niche concept.
Well, 'The Girl in the Trunk' being a Kuroshitsuji fanfic, it might explore unique storylines within the Kuroshitsuji universe. It could focus on a girl's journey or adventure that somehow involves being in a trunk. Maybe it's a mystery - like she's trapped in there for a reason related to the dark and complex world of Kuroshitsuji, perhaps she's a key to some hidden plot or has some special power that makes her situation important.
In terms of plot, these fanfictions might explore different scenarios. For example, a male oc could be inserted into the main storyline, perhaps becoming an ally or a rival to the main characters. This can lead to interesting twists and turns as they interact with Sebastian and Ciel.
I haven't read this specific 'commands and carresses kuroshitsuji fanfic' in detail. But generally, in Kuroshitsuji fanfics, 'commands' might refer to the hierarchical relationship between characters, like Sebastian following Ciel's commands. 'Carresses' could imply a more tender or emotional aspect, perhaps showing a different side of the characters' relationships that might not be as prominent in the original series.
The timing of Kuroshitsuji manga updates isn't fixed. Sometimes it depends on the author's schedule or publisher's plans. You might want to keep an eye on related fan forums or news sites for any announcements.
I don't have enough information to say exactly who Cap'n Kathy is. She could be an original character created by the fan fiction writer. Maybe she's a pirate - the 'cap'n' part could suggest that - who has some connection to the wizarding world of Harry Potter.