When the pair went out to watch the fireworks, Koyuki reveals her feelings of wanting to give up on life, but by meeting Hakuji she became happy and wanted to live out her life. Following her confession, she proposes to Hakuji who agrees to grow strong and be with her for the rest of her life.
HakuKoyu is a ship that isn't as noticed by the fandom, unlike the other canon ships such as TanKana, ZenNezu or ObaMitsu. However, most fans love them and enjoyed their love story, which showed their deep care for each other. It is one of the most loved Akaza's ships and his only famous het ship.
It was later revealed that Akaza's desperate and stubborn pursuit of strength was to heal his sick father and to protect the ones he loved and cared about, namely his fiancée Koyuki and his teacher Keizo.
Koyuki was able to heal and live with the help of Hakuji and her father, she recovered two years later and became engaged to Hakuji.
Despite losing his memories, Akaza was noted to have subconsciously retained his strong feelings for Koyuki, this is seen where Doma noted that Akaza absolutely refused to kill and eat women during his hundreds of years as a Demon, despite his obsessive desire for more strength and power.
Despite being a blood-thristy demon who has murdered several people, he has a set of principles he adheres to. One thing that Demon Slayer fans have noticed is that Akaza refuses to eat or kill women. Additionally, the Demon King, Muzan, gave Akaza special permission to do so.
Doma, as apathetic as he is, considered him his "best friend", seemingly ignoring the contempt Akaza possessed. His carefree and bubbly personality is in stark contrast to Akaza's headstrong and aggressive nature.
There is hostility between Kokushibo and Akaza. He doesn't get along with Akaza, since he sees him as a weakling who disrespects Kizuki who are of a higher ranking than him.
Shizuka is seen often teasing Sanemi and making him annoyed, nevertheless, the two had still created a strong bond and relationship with each other. Eventually, after knowing each other for a while, Shizuka finally ended up having the courage and confessed, leading to them getting married after awhile.
RenGiyuu is the slash ship between Giyuu Tomioka and Kyojuro Rengoku from the Demon Slayer fandom.
EnZan is the slash ship between Muzan Kibutsuji and Enmu from the Demon Slayer fandom.
Akaza was also one of Muzan's favorite demons out of all his subordinates. The reason behind this is Akaza's extreme loyalty to his master. The Upper Rank Three demon was always sent away on special missions, something the Upper Rank 1 and 2 were often denied of.
Since Akaza became a demon, he's been a loyal subordinate to Muzan for centuries. However, Akaza held no respect, awe, or hatred towards him, seeing Muzan as an order giver. while seeing himself as a loyal follower. Despite his loyalty to Muzan, Akaza had a personal code of honor.
Tanjiro decapitates Akaza with the Hinokami Kagura: Setting Sun Transformation. Akaza was bewildered, wondering how Tanjiro did not have any fighting spirit, comparing this feeling to fighting against a plant. He acknowledges that Tanjiro surpassed his speed.
Over a century ago, Akaza was a human by the name of Hakuji before being turned into a Demon personally by Muzan.
Seeing that he still thought highly of him even after his transformation, Kokushibo couldn't help but shed a tear. Unable to truly sever his bond with his brother, he decided to keep the flute.
He was so afraid of death that he allowed himself to become a Demon and therefore immortal. This makes him one of the few known Demon Slayers to defect and turn to become a Demon. In doing so he abandoned a wife and two children, though unlike many new demons he did not slaughter the vestiges of his human family.
The only Demon he despises the most is the Upper Rank Two: Doma. It is quite a shocker that the second most potent Demon in the Demon Slayer is not Muzan's favorite.
Doma is one of the most ruthless and insanely strong demons under Muzan Kibutsuji. As Upper Moon 2, he proves to be the absolute antithesis of Akaza. Moreover, their contrasting personalities as demons or mannerisms of rising up in the ranks are the major reasons for Akaza's hatred towards Doma.
Doma is always smiling and acts very friendly, but this cheerful, caring nature is simply a facade. He states that he cares for his fellow Upper Moons and even cries when he learns that Akaza died, though, in fact, he doesn't feel anything for them.
Akaza outclasses Nezuko in all aspects except one: sun reststance. Unlike Akaza, Nezuko has conquered the sun, making her pretty much impossible to kill w/o demon-reverting medicine.
Shinobu Kocho's tragic backstory is one of the most heart-wrenching in Demon Slayer. She and her sister, Kanae, were orphaned at a young age after their parents were killed by a demon.
The first syllable in Akaza's name contains the the kanji that stands for gentle and docile. An individual who's believed to be gentle and docile shouldn't really have a scowl on their faces. This could be a major reason why Akaza was portrayed as a character that always keeps smiling in Demon Slayer.