So we know he has a Synchro monster, so he must have a Tuner. And it’s a cute little guy.
Meet Choujyuu Musha Horaga-E (Something like Superheavy Samurai Horagai). The Horagai in this context is a war horn used during the feudal era.
And yes, Susano-O is armed to the nines.
Source: Maxut, Weekly Shonen Jump