Complex sentence: Tadashi dragged her back to Uncle Koyanagi's lab, but when she escaped outside again after thinking Tadashi was now attracted to Ms. Yoshiyama, she was attacked by the other creatures.
Split into simpler sentences: Tadashi dragged her back to Uncle Koyanagi's lab. But when she escaped outside again after thinking Tadashi was now attracted to Ms. Yoshiyama, she was attacked by the other creatures.