Complex sentence: Cobb is approached by the wealthy Mr. Saito (Ken Watanabe), Cobb's last extraction target, asking them to perform the act of "inception", planting an idea within the person's subconscious mind.
Split into simpler sentences: Cobb is approached by the wealthy Mr. Saito (Ken Watanabe), who had been Cobb's last extraction target. Saito asks Cobb and his team to perform the act of "inception", planting an idea within a target's subconscious mind.