A list of subclasses found in the Log Horizon TRPG rule book and other official material. Their names may differ from those listed on the Subclasses page, but for the purposes of the TRPG translation, we will be using this list.
Each entry includes the English name, the Japanese name, what (if any) skills within the TRPG that subclass benefits from, as well as any other miscellaneous notes (such as examples of characters with those subclasses, or noting a common translation from other sources). Note also that the TRPG book doesn't really add any new information for subclasses as is, though the Subclass Supplement includes some skills and items related to certain subclasses.
If a skill is listed in italics, then the class is referenced as a Connection in the skill, granting a benefit to the owner if they have a Connection to someone with that subclass. Otherwise, it requires the sub class in order to function, or otherwise provides a benefit for having that subclass yourself.
A note on Astrologer: This sub class is likely a direct reference to Star Sibyls from FFXI, whose prophecies are known as 星詠み in Japanese, and take the form of poetry as is implied by Situation Box: High Society.
A note on Prostitute: 娼 is an archaic word meaning 'woman who sings and dances to entertain others' (somewhat like a geisha). Nowadays it means 'prostitute,' but Mamare has stated that in Log Horizon it has the classical meaning.
Dragonslayer, Giant Slayer, Vampire Hunter, Undead Killer, etc; this sub class is a special kind gained through killing a lot of a specific type of enemy. It isn't actually mentioned in the TRPG book, but it's worth noting anyway.