blabla100:
I am not sure how the chinese translation for it is exactly

The lyrics do not imply that Chi Chen has to be "the one" in A Heng's eyes and heart. What the song asks is that he can exist in her eyes and heart. There is no allusion to exclusivity.

哦也罗依哟
请将我的眼剜去
让我血溅你衣
似枝头桃花
只要能令你眼中有我

哦也罗依哟
请将我的心挖去
让我血漫荒野
似山上桃花
只要能令你心中有我

兄弟们
我死后请将我埋在她的路旁
好让她无论去哪儿
都经过我的墓旁

O ye luo yi yo
Please cut out my eyes
So my blood splashes on your robes
Like peach blossoms on the branches
As long as I can exist in your eyes

O ye luo yi yo
Please take out my heart
Let my blood spill in the wilderness
Like peach blossoms on the mountains
As long as I can exist in your heart

My brothers
When I die, please bury me by her roadside
So that no matter where she goes
She will pass by my grave


But that being said, Chi Chen, as you said, asks, only for a sincere, true love from A Heng. It did not matter to Chi Chen if she was married to Shao Hao and had a child with him. For his love for her, he learnt forbearance, respected her choices and curbed his love for 400 years, waiting only for the day when she would openly acknowledge her love for him.