Emerald and Ruby first meet in volume 2 when Ruby accidently runs into her, Mercury and Cinder. Emerald then helps her up after she falls to the ground. Later when the two are watching Pyrrha and Mercury fight, Ruby excitedly and happily looks at Emerald and smiles at her. Emerald smiles back, but once Ruby turns her head towards the fight, Emerald makes a disgusted look on her face.
Between meeting near the end of the second semester and the beginning of the Vytal Festival the two develop a strong "friendship". When Team RWBY go out for lunch to celebrate progressing to the next round in the Vytal Festival, Emerald appears to give Ruby her wallet she dropped, though it was most likely pick-pocketed from Emerald in the first place. Emerald congratulates Team RWBY on their win which makes Ruby blush and fumble with her words. Ruby invites Emerald and her team to their victory lunch but she declines. Afterwards Emerald vents her frustration with having to pretend to be friends with Team RWBY, not understanding how they can keep up a constant positive attitude.
The two do not interact directly during the fall of Beacon but Ruby finally becomes aware that Cinder and the rest of her team are responsible for Grimm invasion. Ruby and Emerald finally meet again months later at Haven where they fight against each other as both their teams try to gain the Relic of Knowledge. She then asks Emerald why she's doing this to which Emerald replies, "I don't care about Salem, but I owe Cinder eveything". She then tells Ruby if she wants to fight Cinder so badly then to go right ahead.
The two are then reintroduced to each other in Volume 8 chapter 10. When Ruby sees Emerald again she immediately gets angry and is about to take out her weapon to attack her before Oscar stops her. In Chapter 11, Emerald refers to Ruby as "Miss Hero" and says that if she doesn't have an answer, then there is no answer, implying that Emerald believes that Ruby will always have a plan and the answer to a problem. When Ruby gets frustrated and declares that they're in the exact same spot they were in the day before, and runs out of the room, Emerald watches her with a saddened expression and even turns and makes a move like she might follow before staying still. After the group manages to save Penny, Emerald responds to Ruby's earlier "we're in the same place" comment, and tells her "I think you're wrong, by the way. I highly doubt you're in the same place you started".
Blood Mint is a rarepair within the RWBY fandom. While it's fanbase it small, many who don't necessarily ship Blood Mint still believe that Ruby had a genuine crush on Emerald during their Beacon days as she is the character Ruby has blushed for. Their fake friendship also lends its self naturally into fake dating tropes. Also now that Emerald has defected and joined the allies fans are hoping they'll have more moments together now. It has a small fanbase on tumblr.
- Their ship name comes from Ruby being the blood since blood is red like Ruby, and Emerald being the mint.
- Both of them are named after gemstones.
- Purrloined Petals — the ship between Ruby Rose, Blake Belladonna, and Emerald Sustrai
- Jade Rose — the ship between Ruby Rose, Emerald Sustrai, and Mercury Black