ZenNezu

"I will protect you, Nezuko-chan."

- Zenitsu to Nezuko after saving her.

ZenNezu is the het ship between Zenitsu Agatsuma and Nezuko Kamado from the Demon Slayer fandom.

Canon
Before seeing her but knowing already that she was a demon, Zenitsu protected Nezuko from Inosuke because Tanjiro said that she was important to him.

When Zenitsu sees her for the first time and discovers that she's a cute girl, he quickly gets mad at Tanjiro because he thinks that Nezuko is actually his girlfriend instead of his sister. Later, when the misunderstanding is clarified, it is shown that Zenitsu quickly fell in love with Nezuko and tries to catch her attention by running after her or giving her flowers. He's shown to be deeply fond of her even on a short period of time, since on the Natagumo Mountain he refers to Nezuko as "the person he wants to protect" and she's his main motivation to run into the forest, claiming that Tanjiro is a moron for bringing a girl into the danger.

While he fights with his kasugaigarasu Ukogi (Chuntaro) he mentions that Nezuko is cuter than her.

After the fight against the spider demon in Mount Natagumo, Zenitsu tearfully apologizes to Nezuko for not being able to find and save her. In the manga, on the Butterfly Estate, Zenitsu is shown talking with Nezuko when she's inside her box, telling her about his day and saying he will take her to a flower field, and showing her Shinobu Kocho's goldfish.

In the second chapter of the first Demon Slayer light novel, Flower of Happiness, Zenitsu asks Shinobu’s and Tanjiro's permission to take Nezuko to the flower field as he promised. There he sees a yellow flower and gets sad thinking about his past, when he saved and fell in love with a girl who turned out to already have a boyfriend. However, Nezuko brings him back to the present and cheers him up.

In the anime, Zenitsu asks Tanjiro if Nezuko would not be safer at the Demon Slayer Corps headquarters than traveling with them. In the Mugen Train Incident, Zenitsu has a dream about Nezuko. He is holding her hand to show her a place where peaches are delicious and he says that he will make a flower crown with white clovers for her. There is a river on the way and when Nezuko gets worried about that because she can't swim he offers to carry her and jump so she won't get wet. She agrees as shown in the manga extras (Zenitsu's leap of joy). When Nezuko gets in danger fighting against the train demon, Zenitsu jumps to rescue her in his sleep, claiming he will protect her. Then they fight side by side against the demon. After the train derails, Zenitsu protects Nezuko and other passengers, hugging them. When the sun rises, he helps Nezuko to go back to her box and carries her safely.

When Nezuko conquers the sun and is able to speak again, she welcomes him back to Butterfly state after a mission, blushing a bit. Zenitsu is overjoyed to hear her speaking, screaming loudly in excitement, saying she is amazing and asks her to marry him, promising he will feed her eel and sushi every day.

In the second chapter of the second Demon Slayer light novel, One-Winged Butterfly, during the pillars training, Zenitsu tells his fellow demon slayers that he has a girl he loves, Nezuko, who is waiting for him at Butterfly state. He says she will welcome him back, they will get married, he will feed her sushi every day and buy her a bunch of beautiful kimonos and they will live a happy and blissful life. When Nezuko is turning into a human again, she remembers Zenitsu giving her a beautiful bouquet of flowers, hinting that she remembers their interactions. After the battle against Muzan, Zenitsu asks the Kakushi that if he dies, they tell his wife Nezuko that he loves her and he was brave and was thinking about her until the very end.

When Tanjiro becomes a demon and Nezuko tries to stop his attacks, getting injured in the process, Zenitsu screams in agony, begging Nezuko to stay back and Tanjiro to stop. After Tanjiro becomes human again, Zenitsu tells him he will spend the rest of his life making him atone for what he had done to him and his wife, referring to Nezuko. She looks at him flustered, wondering what he means. After these events, Zenitsu and Nezuko go to live in the Kamado house with Tanjiro and Inosuke, where they are shown to live happily together. They will eventually marry and start a family, having two great-grandchildren by the names of Toko Agatsuma and Yoshiteru Agatsuma between them.

Differences between anime and manga
There are some differences between the anime and manga that may affect people’s opinion about the ship, particularly regarding Zenitsu’s ways.

Wisteria house: In the manga, Zenitsu just nods and bows down to Nezuko. In the anime, Zenitsu chases her across the room.

Butterfly state: In the manga, Zenitsu talks to Nezuko while she is in the box and he shows her Shinobu’s goldfish. In the anime, Zenitsu asks a Kakushi girl to go for a walk with him. In that part of the manga, he just said he would go outside and play.

Demon Slayer Academy: In the manga, Zenitsu says that Nezuko is so cute chewing her bread and that she looks like the protagonist of a Shoujo manga because she is so beautiful. In the anime, Zenitsu drools over Nezuko, Makomo and Shinobu.

Quotes
"If I wake up right now I promise to work harder!! If I were to wake up in the presence of my precious Nezuko, then I'll do anything!! I'll do hard manual labor!! I'll even plow fields!! A whole acre!! No, two!! I promise!!! Let me wake up from this nightmare!!!"

- Zenitsu screaming in Mount Natagumo. "Hey, Tanjiro... You sure about bringing Nezuko along? Wouldn't the safest place for her be back at headquarters?"

- Zenitsu asking Tanjiro about Nezuko's safety. "Please... If I die, tell my wife, Nezuko, that I love her... and that I was brave... and thought of her until the very end..."

- Zenitsu to the Kakushi after the battle against Muzan.

Fanon
This ship is one of the most well-known inside the fandom because of Zenitsu's clear attraction toward Nezuko. A lot of people ships them, they love his devotion to her and want Nezuko to reciprocate his feelings once she becomes a human again. However, on the other hand, some fans dislike it because of Zenitsu's tendency to like a woman based solely on appearance or the fact she's a girl.

In the fandom, they are portrayed a similar way as in the canon-verse. Usually with Nezuko finally returning Zenitsu's affections. Zenitsu is also notably more gentlemanly and has a more mature attitude towards her, leaving behind his playboyish ways (liking every woman he sees) and ultimately decides to settle with Nezuko.

Fandom
FAN ART
 * ぜんねず tag on Twitter
 * ぜんねず tag on Instagram
 * ぜんねず tag on Pixiv

FAN FICTION
 * Zenitsu/Nezuko tag on FanFiction.net
 * Zenitsu/Nezuko tag on FanFiction.net

TUMBLR

Trivia
Zenitsu's voice actors both in Japanese (Shimono Hiro) and English (Aleks Le) seem to support the ship. Hiro Shimono usually screams Nezuko's name at many events and in Kimetsu Radio he mentioned Zenitsu is loyal to Nezuko and that he would use Thunderclap and flash against the pillars for wanting to kill her. Aleks Le made a drawing of Nezuko thinking about Zenitsu in one of his YouTube videos.