Season 1 of Tree of Heaven premiered on February 8, 2006.

Hana is a bright young girl who lost her father at a young age. When her mother returns to Japan, she comes with her new Korean husband and his son Yunsuh. Yunsuh’s mother died during his 10th birthday and after her death, he becomes autistic. While Hana is fond of her new step-brother, he wants nothing to do with her. When their parents leave on their honeymoon, Hana’s mother leaves the children with her deceased husband’s sister who will manage their inn during the trip. While they are gone, the aunt and her daughter Maya abuse Hana and make plans to sell the inn in order to pay for gambling debts and college. Despite all of this, Hana finds comfort in her brother who begins to open up to her and eventually speaks after his 20th Birthday and the day his mother passed away. Yunsuh's mother died on the same day as he was turning 10, 10 years ago. As they start to have feelings for one another, Hana is afraid to love him. She soon leaves with her "senpai", Fujiwara Ryu, who also likes her. Later on, Maya gets jealous, and decides to make Hana's life even more miserable.