This Achievement can be obtained on the first level of the game "
Kanazawa City".
Near the end of the level just before you blow up the supply building use "
Mugen" to take one of the smaller explosive barrels in the top right of the final camp and place it just infront of the tent that general Okkoto spawns from. After this is done have the level advance as normal once the general spawns use "
Takuma" to shoot the barrel you place and the achievement will pop.
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