PMs are full, but eh...this doesn't necessarily need to be private since the pressing concern is largely with our characters and where they are in their various journeys.
I know things have been kinda slow in terms of plot progression at this point in time, but might I suggest waiting for a bit before going ahead with this particular reveal? An open challenge is something that everybody should be present for, not just two characters, I feel.
It also just seems a bit sudden, and a little odd that Sakin would openly reveal himself in this manner after staying secretive for so long, I guess. Part of his intrigue so far is that we don't exactly know what he's doing, and we just got one tangible clue with the parasite's remains and Arthur's correspondance about how to find him.
Also since this is a timeskip period, a few players are still trying to get things moving in subquests, including myself.
You've been very patient and I appreciate that, especially with real life really slowing stuff down, but these sub-chapters take time. Given the 7-month jump to this period, us players still need some time to detail where our characters have moved from the beginning of the timeskip to this point. Like, Sub was going to have Parsley undergo the magic training, Totoma and Held are both still MIA, and Inanna who has abandoned the party might need some incentive to return.
Even though the cat's kinda out of the bag, perhaps this current correspondance with Sihn could end a little more ambiguously?