I can give a sorta brief summary. So back before the Inazuma patch, on the southern parts of Dragonspine, there was 3 bottles that drifted there. The theory was it could have been Kazuha who sent those letters to Scaramouche who left Inazuma and hoped to meet him again at Uyuu Restaurant.

Hhmm I see I see I love kzscr but that seems like a stretch 🤔 was it ever confirmed or maybe hinted that Kazuha sent it?