Aether has been invited to a picnic.
Which would not be strange, unless you count the fact that it's a picnic Albedo has set up and has invited not only him and Klee, but the rest of the Knights as well.
"Ah, Traveller," Kaeya calls after him as he strides towards him, carefully stepping over the vines of the Windrise tree so as to not spill his glass of wine. "Albedo's looking for you."
He gestures to the other side of the tree, beyond where Lisa and Jean are sitting down. Albedo's sitting on a root facing the river where Klee is playing with Amber and Eula – or rather, Amber is showcasing her baron bunny so Klee doesn't turn her attention to the river's fauna, with Eula supervising.
"Not every day our Chief Alchemist decides to organise a social event," Kaeya says as Aether gets up. Does he share Aether's unease over Albedo's strange behaviour? "So go see what's bothering him."
Ah, he does.
