However, Jang Hyun-soo's handball gave referee Milorad Mazic little choice but to point to the spot - the number of penalties awarded in Russian Federation consequently surpassing the 13 across the entirety of the previous World Cup - and Vela, who announced the death of his grandfather following the win over Germany, converted.
Carlos Vela gave Mexico the lead with that penalty after Korean defender Jang Hyun-soo blocked Andres Guardado's cross with his arm inside the area, before the nation's all-time leading goalscorer Javier Hernandez doubled their lead in the second half with his 50th worldwide goal.
Mexico lead Group F on six points after two games, having backed up their shock victory against Germany with another display to suggest they can go deep in this tournament.
Hirving Lozano was Mexico's hero on matchday one and the winger proved his worth at the other end in the 12th minute with a superb block to deny Yong. South Korea lost its opening match.
Mexico's ball control kept the South Korean side pinned to their half of the pitch until tactical changes took effect at the intermission.
Mexico held firm, but they also left some goals on the table.
Ki Sung-yueng was the next to test Mexico's resolve, stinging the palms of Guillermo Ochoa with a rasping first-time strike.
Meanwhile, South Korea were condemned to an early exit after losing their opening two matches despite Heung-Min Son scoring a spectacular consolation strike in stoppage time.
Not to be outdone, Cho was at his best soon after, South Korea's goalkeeper lunging to his right to tip Hernandez's goal-bound shot wide.
After 28 games at the World Cup, there have now been 14 spot-kicks, 11 of them converted, and there could be little complaint about this one, coming after a blatant handball by Jang Hyun-soo, Vela stepping up to convert.
With the second goal Mexico tried to shut up shop by sending on the experienced Rafael Marquez for Guardado.
If Germany couldn't crack the Mexican defense, South Korea are going to have an even harder time breaking through.
Just as South Korea were beginning to grow in confidence they fell behind.