Transmigrating to Become a Bewitching Concubine

1v1. The male lead is involved with other women early on, so enter with caution if that bothers you. Later, he devotes himself to her alone. He knows he loves the heroine and stays faithful to her. After Lin Xinyue realizes she's transmigrated, she resolves to live well on the original owner's behalf. With the Thirty-Six Stratagems at her disposal, she's not afraid of any scheme or trick. But why has the male lead's character suddenly changed? Why is the heroine taking the initiative to become her close confidante? What's going on?