Speaking of whichdid the writers forget what Cantus Leakage is? How the fuck was that relevant?
The idea apparently is that Kaburagi Shisei was pretty much immune to any kind of physical attack, but vulnerable to cantus itself (something Saki figured out when she suddenly recalled that he was visibly worried about cantus leakage back when Shun was turning into a Gôma). Instead of using his cantus to move objects around (as usual), the kid used it directly on Kaburagi's body (the "rainbow" over the guy's head is a phenomenon that occurs when canti collide).