I haven't seen this stage yet, so take this with a grain of salt, but I believe this to be art of one of the IRL humans in the Hanakage Yureru Tomizu Stage Musical, being specifically Honami Koetsu (from what I can tell of stage merch by Googling 本阿弥光徳 刀剣乱舞 in any case). Dunno how to tag that, I'll be updating with the musical_touken_ranbu tag momentarily at the very least.