The journey from Lower Realm to the Upper Realm was extremely far, and they needed to pass through the Middle Realm.
After the massacre of the Nine temples, the Middle Realm welcomed a period of peace. Until now, the Upper Realm did not send anyone to take over that terrible mess. Jun Wu Yao had arranged for some of the Night Regime and the accompanying Rui Lin Army to stay in the Middle Realm and secretly observe whether there were other side measures deployed by the Upper Realm.
After passing through the Middle Realm, to reach the Upper Realm, they needed to pass through a seemingly endless sea - the Sea of Death.
