What's important to note here are his two practice swords behind him and their shadows merging with his own/his shadow just casting the shadow of the swords behind him and not his own. For me that is a representation of the swords being an extension of his own body. Which is a regular idea taught to any swordsman.
Related to the Dance's theme. Yumeki is wearing Red to match the Fire Element theme for the Event. I added in a lot of pink to the red for light and shadow, but also it fits Yumeki's recuring Sakura Blossom theme as well.