Complex sentence: Although he mentors all three members of Team 7 early in the series, he concentrates on training Sasuke as the series continues, teaching him his Chidori technique; however, he is unable to prevent Sasuke from leaving the village to seek Orochimaru for greater power.
Split into simpler sentences: Although he mentors all three members of Team 7 early in the series, Kakashi focused on Sasuk'es progress and taught him his personal Chidori. However, he is unable to prevent Sasuke from leaving the village to seek Orochimaru for greater power.