Guan Yu fell in love with Diao Chan upon seeing her for the first time, though it took him a while to win her heart. They officially became a couple in 16th Round, where a more positive Diao Chan confessed to Guan Yu and asked him to become her boyfriend, which he agreed.
Guan Yu has always been in love with Diao Chan since the first day they met, when he first enrolled Dong Han Academy. At that time, Diao Chan and everyone else in school noticed that Guan Yu had a crush on her because of his odd behavior around her (his face turns red every time he sees her); however, Diao Chan did not seem to be interested in him because she said that she did not like it when people fall in love because of appearances, and because Guan Yu fell in love with her in first sight that meant that he fell for her good looks. Even though she did not like him as more than friends, she was still nice to him and treated him as a good friends.
When Diao Chan was kidnapped by Li Ru and Mei Niang, Guan Yu was very upset and also blamed himself for not able to protect her. He vowed to rescue her from the kidnapper and almost succeeded. Unfortunately, when he got to the kidnappers' place, she had already been rescued by Lu Bu. Guan Yu was devastated because he was unable to rescue her like he promised. Not long after, Guan Yu was heart broken when he found out that Lu Bu and Diao Chan had started a relationship.
After Diao Chan and Lu Bu's relationship fell apart, Guan Yu became closer to her, despite she was still in love with Lu Bu. He indicated that he only wanted what's best for her, not what he wanted from her. During this time, Guan Yu often protected her from harm and provided her safety. Eventually, he became an important part of her life; however, she only thought of him as an important friend.
When Diao Chan fell under the influence of Bian Hen Da, she openly confessed her feelings for him and they became a loving couple. When they started their relationship, they made seven promises to each other. Not long after they became a couple, Guan Yu drank Forget This, Forget That, Forget Emotions Potion and accidentally forgot his relationship with Diao Chan. Diao Chan was very heartbroken and even attempted to commit suicide by drowning herself to the sea. Luckily, she was saved by Lu Bu. Sun Shang Xiang and Xiu then told her about the potion that Guan Yu drank and gave her a new edition of 'Bian Hen Da' that changed her to become more optimistic. After that, her relationship with Guan Yu went back to normal.
Not long after that incident, Diao Chan suffered from side effects cause by 'Bian Hen Da', which would eventually led to her death. Guan Yu was very devastated when he heard this and he kept holding her hand when she was hospitalized. He refused to let go of her hand and refused to eat, sleep, or take a shower for a week. After Diao Chan was "cured" from the side effects she still chose Guan Yu over Lu Bu because the one she loved was Guan Yu and her feelings for Lu Bu was mainly out of gratitude for him rescuing her.
When Guan Yu suffered from the side effects of Zhen Cha Jing and Hao Cha Jing, Diao Chan was very worried and upset. After she found out that Guan Yu only had one year to life she became extremely sad and often cried. Fortunately, Guan Yu was able to regain his powers back with help from his friends and also able to reverse the side effects so that he was able to life long. This made Diao Chan very happy and they once again became a happy loving couple.
Not long after, Diao Chan found out that her father, Wang Yun, was killed by Dong Zhuo. Knowing that possible death might befall to Guan Yu, she decided to participate in the battle against Dong Zhuo. But because she knew her inability of kung fu practice gave her the most deathly disadvantage, she ended her relationship with Guan Yu by giving him a potion to erase his memory of her to protect him from heartbreak if she died in the battle.
After Diao Chan disappeared with Dong Zhuo, Guan Yu began to experience memory gaps and emptiness. His memory was recovered when he was reminded of a time when he was told to draw the person he loved the most. After his memory recovered, he departed to Liu Cheng to wait for her return.
One night, he had a dream about a happy Diao Chan. After he had this dream, he realized how much she would have wanted him to be with his friends rather than drifting into loss. Because of this dream, he decided to return to his friends and fought along side them.
By the end of the series, Guan Yu was back in Liu Cheng to wait for Diao Chan to return. While he was talking to Xiu by using the Dimensional Cellphone, he saw a girl that was injured and offered to help. It turned out the girl was Diao Chan and they were finally able to reunite with each other.
The Seven Promises of LoveEdit
Guan Yu and Diao Chan have made seven promises of their love.
- No arguments.
- No pointing at the other's weakness.
- No lies.
- No angry outbursts for unnecessary reasons.
- Hold each others' hands least once per day.
- Never mind if the other is overweight.
- Say "I love you" everyday, no matter what.