douma being the tickle monster of the upper moons has never been defeated hell not even by kokushibo, nor muzan BC muzan didn't really care... he adored getting to make each of his "friends" happy after a hard night of work, his favorite victim was akaza, no one actually knew if douma was ticklish or not considering douma didn't know either, one day he was tickling rui making the poor spider boi squirm until u, a new upper moon (another upper moon 2) challenged him to a duel, aka a tickle duel

aww~ a challenge? well I would be delighted to!

he placed rui down and made his way over to u getting into a position for the duel