Complex sentence: In the Kamakura period, Jito were chosen from amongst the Gokenin (the shogun's vassals), who governed military affairs, and handled the taxation and administration of the manor they were appointed to, and directly administrated the lands and the farmers of the manor.
Split into simpler sentences: In the Kamakura period, Jito were chosen amongst the Gokenin (the shogun's vassals) who governed military affairs. Jito handled the taxation and administration of the manor to which they were appointed, and directly administrated the lands and the farmers of the manor.