Executed by performing two quarter-circle forward motions and pressing punch, the attack is a small Shoryuken followed by a large one. If the punch button is repeatedly tapped, the attack will hit more times, and can reach damage levels of around 30-35%.
It can be used as an anti-air attack, but does not hit as many times in this case. Due to the limited range that it has at the beginning, it is not easily used as a counter.
However, it is possible to use a full Super Art Gauge and finish a combo by chaining together two consecutive Shoryu-Cannons.
Sean cannot use the Shoryuken normally; he is usually capable only of a Dragon Smash. It is likely that this attack represents what he can do only with extreme concentration.