The scene stars our fencer trained in Marozzo dueling one trained with MS I.33. The weapons are sword and buckler.
The worthy foe cuts into Underarm, which they call First Ward. Our fencer responds by mutating into Coda Lungs e Larga. The wide, low guard serves two purposes, the first being to invite an attack.
If the opponent begins a cut he will have to step forward to reach our fencer. When he does so our fencer steps to the right and cuts the newly outstretched leg.
I mentioned two purposes for the low blade. The second is to make this action a Mezzo Tempo or middle time attack. Only a flick of the wrist is needed to land the cut, allowing you to interrupt their action.
To recover safely, retreat or step past while bringing up the sword into a middle guard such as iron gate.