Complex sentence: After losing, she quit Team Galactic again, causing Jupiter to explode the room she was in, apparently killing her; later it turns out that Jun had saved Mitsumi and Eevee at the last second by protecting them from the explosion with Light Screen.
Split into simpler sentences: After losing, she quit Team Galactic again, causing Jupiter to explode the room she was in, killing her. Except later it turns out that Jun had saved Mitsumi and her Eevee at the last second by protecting them from the explosion with Light Screen.