Complex sentence: As Dogen had plans to force Mitsuomi Takayanagi into fighting Shin, Mana plays her role by starting an affair with Mitsuomi and actively spreads it around.
Split into simpler sentences: As Dogen had plans to force Mitsuomi Takayanagi into fighting Shin, Mana plays her role. She starts an affair with Mitsuomi and actively spreads it around.