Complex sentence: Soon after her arrival she meets with her grandmother, which is soon explained that she has to continue the role of ancestor princess Tamayori, to seal the sword Onikirimaru with the help of her five guardians.
Split into simpler sentences: Soon after her arrival she meets with her grandmother. It's later explained that she has to continue the role of ancestor princess (Tamayori), to seal the sword Onikirimaru with the help of her five guardians.