Complex sentence: Chun Li is on a mission to find out what happend to the stronger warriors she thinks it relates to Shadow Law acts, she also vows to help find Ryu's Brother, Sakura couldn't have come because of the accident she had back at the Tournament.
Split into simpler sentences: Chun Li is on a mission to find out what happened to the stronger fighers who have gone missing, thinking it relates to ShadowLaw. Sakura was unable to come because of the accident she had back at the Tournament.