Complex sentence: Chibiusa befriends a mysterious girl named Hotaru Tomoe, daughter of Mugen Academy founder Professor Tomoe, who is later revealed to be a key figure of the Death Busters.
Split into simpler sentences: Chibiusa befriends a mysterious girl named Hotaru Tomoe, who is the daughter of Mugen Academy founder Professor Tomoe. He is later revealed to be a key figure of the Death Busters.