Complex sentence: Soon after, unidentified ghost-like spirits begins to appear in Karakura Town, before a mysterious Soul Reaper named Senna appears and begins to slice through the spirits flawlessly.
Split into simpler sentences: Soon after, unidentified ghost-like spirits begin appearing in Karakura Town. Suddenly, a mysterious Soul Reaper who calls herself "Senna" appears and begins to slice through the spirits flawlessly.