Complex sentence: Dimensional Witch Yūko Ichihara instructs him to go with two people who also want to accomplish their respective wishes, and, in the search of Sakura's memories which were scattered in various worlds, and gathering them will help save her soul.
Split into simpler sentences: Dimensional Witch Yūko Ichihara instructs him to go with two people, and. They search for Sakura's memories, which were scattered in various worlds, as gathering them will help save her soul.