黑帮大佬和我的365It is a story of a mistress who comes back for her revenge after enduring all kinds of mistreats from her husband's wedded wife. The resentment between two love rivals is passed on to their descents and grows into a war between two bloodlines. Onnapa is a mistress of a millionaire who owns the biggest flower business in the country. She has endured all kinds of mistreats by her husband's lawful life, Kannika, for years. When their husband dies, Kannika kicked Onnapa out of their home. Onnapa is enraged by the injustice and furious at Kannika. Although more than 30 years have passed, the resentment in Onnapa's heart has never eased off. Now, it is passed on to her daughter and grandchildren. Along with her daughter - Onsalao and her grandsons - Worakorn and Worawet, Onnapa comes back to take her revenge and reclaim things that should have been hers. Onnapa starts a war with Kannika and her descents including Kannika's daughter - Thantawan, and her grandchildren - Mintra, Nonsee, and Iris. Filled with trickery, deceit, and betrayal, how will this war end?