This was kind of reassuring, as far as things went, because he was pretty sure Tomoe didn't have anyone else's best interests in mind, except maybe Acheron's.
As for how close Acheron was with Lupin... Nico wasn't really sure how exactly that had happened. Acheron had such a stoic demeanor, and Lupin had enough bravado for five whole Pokemon, let alone one little guy who was the size of a chew toy compared to a lot of the other Pokemon they fought against.