Kochou Sisters

Shinobu and Kanae
Shinobu and Kanae are extremely close and have a strong sister like relationship due to the fact that both of their parents died and they both had to rely on each other. Shinobu looked up to Kanae and often turned to her whenever she was having troubles to which Kanae would always educate her politely. Their bond is so deep and caring that they both took an oath to protect other's from going through the same pains that they did after they both survived a Demon Attack that killed both of their parents. Their relationship is quite strange however due to Kanae often making lighthearted weird remarks without much thought first to which Shinobu would worry about her sisters weird behavior and soon become confused. Despite this however Shinobu still cares about her sister deeply and trusts her even if she doesn't agree with her. As seen when the two adopted and ran off with their new little sister (Kanao)

Later however, Kanae's deep love for her sister shown the brightest in her final moments after fighting Doma. Kanae begged Shinobu to leave the Demon Corps and go live a free and happy life with Kanao since they already knew how to protect themselves should the time come when an unexpected Demon Attack happened. Kanae states that the only thing that would truly make her happy is knowing that Shinobu can live a happy live. Shinobu then tells her sister that she couldn't possibly due that since they both took an oath and begged her sister to tell her which demon did this to her so she can make them suffer and swore eternal vengeance against whoever did this to her sister. They later reunite in the afterlife after Shinobu is slain by the same Demon that killed Kanae feeling blessed that Kanao could do what they couldn't.

Shinobu and Kanao
Despite Shinobu being the one to impulsively buy Kanao out of slavery, she quickly becomes frustrated and annoyed when she found out that Kanao could not make her own desicions. Saying that Kanao could be dangerous to her and other people. Overtime however, Shinobu began to warm up to Kanao and eventually began to view her as the true younger sister that she was. During Kanae's funeral Shinobu comforted Kanao and was understood her inability to cry. Much to the slight surprise of Kanao seeing as though she knew how close the two were but never the less still appreciated Shinobu's comfort.

Shinobu eventually decided to make Kanao her successor because of her incredible talent as a Demon Slayer. Shinobu taught her how to cut off a Demon's head without remorse and without thinking. While at first she was worried about whether or not this was Kanao's true will or not, Shinobu was relived when Kanao herself said that she wanted to and would be honored to train under Shinobu. Shinobu is incredibly happy and touched by this and teaches Kanao everything she can.

Shinobu and Kanao hold a great amount of trust in each other. Shinobu even told Kanao that if necessary then use Shinobu as a sacrifice to avenge Kanae and to carry out Shinobu's wish. She also becomes extremely protective over Kanao due to her already losing one sister she refuses to let it happen again under her watch. Inosuke mentions how Shinobu gets "Really Mad" whenever Kanao gets hurt in a sense that doesn't involve training. It should be noted that Inosuke had a hard time understanding human feelings at the time so Shinobu's anger seems quite genuine and sincere. Shinobu even expresses her worry towards her using the Flower Breath's Final Form and how she could lose her sight even though Shinobu was close to death. After Shinobu dies at the hands of Doma's, Kanao with the help of Inosuke, manages to kill Doma and avenge the death of both of her sisters. Kanae and Shinobu then thank Kanao and give her their blessings right before parting into the afterlife which causes Kanao to cry for the very first time in her life. After their deaths Kanao keeps both of their butterfly clips as a reminder that they will always be there for her and promises herself that she'll hold them in high regards for as long as she lives until she can reunite with them in the afterlife.

Kanao and Kanae
Kanae was the one to take a particular interest in Kanao when she saw that she was about to get sold away to slavery. Along with Shinobu they both ran out of there with Kanao. After that they trained her at the butterfly mansion and taught her how to slay demons and defend herself. Kanae defended Kanao whenever Shinobu got irritated at Kanao not being able to make decisions for herself. She said that overtime Kanao's heart would blossom and she'll be able to make her own decisions soon enough, it would just have to take a little time. In order to help out Kanao she gave her a coin that she could use to make decisions whenever she is unable to decide stuff all by herself.

Later after Kanae's death Kanao is deeply saddened at the fact that one of the few people to ever care about her was gone. During Kanae's funeral Kanao found herself unable to cry no matter how hard she tried. But she still wears one of Kanae's hairpins as a memento. She expresses deep remorse and guilt that she couldn't even cry at her own sisters funeral. However due to the comfort of Shinobu she was able to feel some sort of closure.

Fanon
The ship sailed as a result of them all being sisters and how close their bond was. Fans loved how kind and understanding Kanae was to Kanao and a lot of other fans love how Shinobu underwent such good development with Kanao that she was worried about her even when Shinobu was the one in pain. It is hardly ever shipped romantically seeing as though there's a decent age gap between them and they're all siblings.