Sun is introduced winking at Blake in slow-motion as he runs past, with a choir of angels in the background. After Blake accidentally reveals she is a Faunus to her team, she flees and runs into Sun. They spend two days together before she confides in him about her history with the White Fang, which she does before she confides in any of her teammates. Afterwards, Sun helps Blake fight Roman Torchwick and his White Fang thugs.
Just before the food fight, Sun can be heard telling Neptune how amazing Blake is. Later when the team decides to investigate, Sun and Blake are made partners for it. Blake goes with Sun to the school dance where she can be seen dancing and laughing with him all night long.
After Sun's victory in the tournament, he points to Blake in the stands and she blushes, affectionately calling him a dork. Sun is also the first character to know that Blake has left Beacon at the end of the season, and he informs the others of it.
After Blake runs off, Sun chases after her to help her with whatever she's doing. During their fight with the dragon Grimm, they both catch each other in the bridal position, where Sun even playfully exclaims "My hero!". When Sun catches Blake, he pokes fun by saying, "This is the part where you say it." to which Blake rolls her eyes. Sun is later introduced by Blake to her parents, Kali and Ghira. They have tea together and Kali admits that she "likes him" (Sun) to Blake, to which Blake herself gets flustered. When Sun is later recovering from being stabbed by Ilia, Blake also calls him "my hero" in return, a callback to him rescuing her earlier in the volume.
Sun continues to help Blake fight the White Fang while in Menagerie, as well as restore it to its once more peaceful ways. They are seen having another tea "date", just like in Volume One, and they blatantly flirt while talking about more serious issues. Blake also admits that she tends to describe people through just one word. She has yet to decide on a word for Sun, but as of now, said word is "earnest". At the Battle of Haven he encourages Blake to help her teammates and later again urges Blake to reunite with her friends. Right before this, Blake and Sun also briefly fight Adam together. When he runs off, Sun is about to follow him, but Blake doesn't want to, fearing that they might be lured into a trap. When Sun is about to go back and fight the rest of the enemies on his own, Blake stops him by putting a hand on his shoulder and telling him to be careful, to which he smirks and replies "No promises". Blake then turns her head and looks down to smile before running to help her teammates.
After the Battle of Haven, Sun sees Blake off at the train station as she heads off to Atlas. Blake kisses him on the cheek as a farewell, and he leaves the station with Neptune in tow. Neptune comments that it feels like he's giving up on her but Sun corrects him in saying it was "never like that" and he's just happy to have been able to support Blake, because that was what she truly needed before anything else.
Albeit considered non-canon, RWBY Chibi counts more than one BlackSun moment throughout its seasons. For example, Blake and Sun are seen going on an implied date to the library in season two. Moreover, Sun is also seen asking Blake out again at the end of season one - she accepts gladly after teasing him a bit ("That's the cheesiest thing I've ever heard"), but they are interrupted by Neptune, who takes Sun away, much to Blake's sadness. During this scene, the audience cheers loudly and even goes "aww/woo!" when Blake accepts Sun's invite. In season three, Sun is displayed in one of Blake's dreams, together with Neptune, Velvet, the shopkeeper, and a fish.
Sun and Blake are also seen recording a beauty vlog together and having a lot of fun with it. Blake indirectly calls Sun a dork again during said vlog (reference to the blushing scene in Volume Three).
This ship sailed in the first volume and had a large push throughout the first five volumes. BlackSun is the primary rival to Bumbleby (Blake Belladonna x Yang Xiao Long), which sadly lead to a big, still on-going shipwar. Those who don't like BlackSun will often ship Sea Monkeys (Sun x Neptune), Sunflakes (Sun x Weiss), or Strawbana (Sun x Ruby) instead.
BlackSun is believed to be Blake's second biggest ship and Sun's biggest. On Ao3 it is Blake's fourth most written-for ship and Sun's second.
- Yssa Badiola, voice actor for Ciel Soleil (RWBY) and lead animator at RoosterTeeth, is a hardcore BlackSun supporter. On her Tumblr blog she has posted a bunch of drawings of the two together, and even talked about them on RWBY Rewind more than once.
- Included in the RWBY Volume Four soundtrack is the main BlackSun leitmotif/song, called "Like Morning Follows Night". One of the verses from Sun's POV specifically says that he'll wait until Blake "will finally see the love that is him". Hence why it is believed that one day, as a callback to Blake assigning everyone a word in Volume Five, Sun's will be "love" and not "earnest" anymore.
- Still in terms of songs, another BlackSun-related composition is Not Fall In Love With You (from the Volume Three soundtrack). The author of the song, Jeff Williams, stated that the track is not related to any couple in particular, yet, in the show, it played only once, specifically during the scene in which Sun winks at Blake and she blushes. Hence why many fans think of it as an early BlackSun anthem.
- BlackSun is characterized by many callbacks and parallels. For example, Sun tells Blake that she "looks better without the bow". Later on, when the two are going to the dance together in Volume Two, Blake tells Sun that "he looks better with a tie". And so on.
- During the "date" scene in Volume Five, Blake and Sun are seeing drinking from open coconuts while sitting at a table. Each of their drinks has a little umbrella (typical drink decoration) and, coincidentally, Blake's umbrella displays a pattern very similar to Sun's tail, while Sun's displays a pattern made of moons and stars (very close to Blake's whole theme and the fact that she's represented by the night in the song called Like Morning Follows Night).
- So far, Sun is the only person that has been given what the fandom calls a "kitty" smile from Blake ( :3 ) at the end of Volume Four.
- During a Q&A session on Tumblr, RoosterTeeth revealed that Blake's second favorite anime is called Bananya , which interestingly features a cat inside a banana.
- Arryn Zech, Blake's voice actor, stated at RTX 2018 that she could easily get behind BlackSun (despite being a big Bumbleby supporter).
- Moreover, she also stated at Supernova 2018 that as far as the show goes, she knows that Sun is meant for Blake. 
- Arryn has also compared Blake and Sun to Marinette and Adrien from the show Miraculous Ladybug, who form the semi-canonical pairing of Adrienette .