The blowing-candles-out thing they're doing is part of the hundred tales game, where you sit in a circle and tell scary stories, blowing out a candle at the end of each one. (Blowing out the last candle completes the ritual and invokes spirits drawn by the spooky atmosphere, of course.)
I already got spoiled but I don't mind
About Iruma's weapon:
A bow. Becoming an archer is quite fitting for Iruma. They attack from a long distance and are in danger at close range, but Iruma has 100% chance of evading so he will be safe even if the enemy gets close.... Imagine if Iruma is able to shoot arrows while dodging all the attacks, that would be OP as fuck.