Complex sentence: After the "Arc" successfully take over Second earth from the ignorant High Counsel, Marlene heads down to earth in search of Yuji, when she finds him his B-cells are already beginning to activate and he begins to go berserk as a killing machine.
Split into simpler sentences: After the "Ark" successfully take over Second earth from the ignorant High Counsel, Marlene heads down to earth in search of Yuji. When she finds him his B-cells are already beginning to activate and he begins to go berserk as a killing machine.