one thing i need the clarification from the LN reader.
cant player just leave their guild, or do they need guild master's permission for that? i mean, cant Shiroe just ask the twin to leave their guild and join Log Horizon? if they do it in the city, no harm can be done to both of them, as the city is PK-free

i think the main reason why the NPC is worried is because the player started to be independent without them. The food can be made(even got taste), even the basic ingredient can be farmed alone right now as the area is safer now. So basically the NPC is afraid that this new changes is less beneficial to them, as the only job left is something like administration in guild hall, which of course the pay is cheap.
just my opinion

Macam bangla la, work hard but got gaji ciput, need to mogok a bit, mintak raise....