Spring Grass or (Miwa) is the daughter of Blacktooth and sister of Bluestone and Waterfront. Spring Grass or (Miwa) was a handmaid of Ji Ning. She took care of Ning since Ning was little up until she was given freedom from Ning and was allowed to go back to the newly created Blacktooth tribe with her father.
Spring Grass's father is Blacktooth who was the son of the tribal chief of Blacktooth tribe. The Blacktooth tribe was attacked by Blood Mosquito tribe when she was little and her grandfather and sister died in the attack. Spring Grass fled with her father. Her father wanted to get revenge on the Blood Mosquito tribe and decided to sell Spring Grass to the Ji clan so she will have a good life and that she won't be involved with his revenge.
She was first introduced as Ning's maid and was seen to help a four year old Ning get changed along with Autumn Leaf. She also alongside Autumn Leaf carry books for Ning. In fact she also was the first person along with Autumn Leaf to helped Ning to read. Later on when Ning at the age of 10 goes out on a stroll to West Prefecture City, she accompanies him where Ning buys his Darknorth Swords.
Spring Grass is next seen when her father comes to the Ji clan and talks to Ji Ning about buying back Spring Grass's freedom. She is very emotional at seeing her father after so many years. Ning agrees to free her for no cost and she gains her freedom and goes back to the Blacktooth tribe with her father.
Spring Grass was sad for leaving Ji Ning but she gets over it when she interacts with her tribal members and her two younger brothers Waterfront and Bluestone. She looks for the day when Ji Ning would visit her in her tribe. Her tribe then gets attacked by Serpentwing and it leads to death of more then half of the tribesman including her younger brother Waterfront. Because of Serpentwing attack the tribal members gets scared and lot of them starts leaving to join bigger tribes for protection. There was a danger of the whole tribe collapsing and this worries Spring Grass's father. Spring Grass worried about the tribe and her father decides to write a letter to Ji Ning in West Prefecture City asking for help but Ning already left the west prefecture city.
Spring Grass then goes to the Riverside tribe along with her father Blacktooth and talks to River He, a powerful figure within Riverside City. They offer treasures to him and ask for his help in protecting the Blacktooth tribe. River He however was not interested in the treasure and wanted Spring Grass as his women but Spring Grass rejects him. He sends his men to capture her but they get defeated by Spring Grass and Spring Grass threatens him by saying her relationship with Ji Ning but Riverside He does not believe her and tells her he would only protect Blacktooth tribe if Spring Grass becomes his women.
After agonizing over the decision for three days, Spring Grass finally relents and decides to be Riverside He's women. However Riverside He attacks Spring Grass when she was completely unprepared and destroys her dantian and after that he mocks her. Spring Grass suffers immensely under Riverside He. She however was able to talk to her father privately and tells him this is her fault and that he is not to be blamed. The current predicament was because of her decisions and she writes a letter to Ji Ning concocting a story about how she met a travelling merchant and decided to marry him. She wanted Ji Ning to have happy memory of her and afterwards she commits suicide through poison.