KevinSu

KevinSu is the slash ship between Kevin Kaslana and Su from the Honkai Impact 3rd fandom.

Canon
Kevin and Su were both members of Fire Moth, an organization of the Previous Era fighting against the Honkai using advanced technology and genetically enhanced soldiers called MANTIS. The two were part of the Thirteen Flame-Chasers, a group of MANTISes who survived the Tragedy of Binding. Kevin and Su are respectively ranked first and seventh in the group.

Previous Era
Before joining Fire Moth, the two were best friends in high school up until Kevin’s disappearance during the Honkai outbreak in Nagazora City. Years pass, and Su becomes a doctor treating patients suffering from Honkai sickness. Despite the workload and mental toll, Su still studied cases relating to Honkai on the side and sent in applications to Fire Moth in the hopes of fighting the disease and the possibility of Kevin being there as a survivor of the Nagazora attack. However, things take a turn for the worse when his mentor, Chief Physician Fall, passes away from Honkai sickness and his application is rejected by the Director of Fire Moth’s Fifth Science Department, Professor Speirs.

Two months pass, and a Honkai outbreak occurs in his city. In lieu of his own, Su drags a fallen girl to safety and inevitably contracts Honkai sickness after shielding her from a beast. The two were saved when Professor Speirs finds them and calls in Kevin, who defeats the Honkai beast in a single blow. Su wakes up in the Fire Moth base to find out that the girl he had protected succumbed to disease. Speirs tells him that he was only alive because of a serum created from the antibodies of 1,000 people who had fallen victim to Honkai and accepts his application to Fire Moth. Su is then given a dossier of Kevin’s activities from the past 5 years as an initiation gift.

After an unknown period of time, Su becomes a MANTIS and manages to locate the 8th Herrscher, playing a great role in her defeat. Despite the victory, many losses were incurred and Professor Speirs, who had become his mentor, was killed. It is unknown whether Kevin and Su had spoken to each other up until this point, but Kevin finds Su holding his mentor’s flask, saddened by his death. Kevin tells him that drinking wasn’t good for his health and informs him that Dr. Mei had invited him to take part in Project Stigma.

A timeskip occurs and the last surviving humans are in a battle against the 14th Herrscher. Two of eight of earth’s strongest warriors had died soon after facing her on the moon. This prompts Su, now the Director of the Fifth Science Department, to initiate Project Sanctuary. Upon learning that Kevin was one of the six who had survived, he rushes to Dr. Mei to inform her himself. However, Dr. Mei’s time was limited, and she passes on her final words to Su before dying of Honkai sickness. Before entering the underground cryogenic pods from Project Sanctuary, Su recalls his promise to Dr. Mei – that he would always remain by Kevin’s side, and to make sure that he never strays from the right path.

Current Era
After 50,000 years, the remaining MANTISes from the previous era awaken and become pioneers tasked to help the humans of the current era in dealing with the Honkai. Su keeps his promise, and since then has been travelling the world of the current era by Kevin’s side for thousands of years. In late 5th century Britannia, the two save a young boy named Arthur from a Honkai beast. Su calms the boy down as Kevin disposes of the beast. Before Arthur could thank them, they disappear into the bottom of the Thames River and Arthur mistakes Kevin as Merlin and Su as the Lady of the Lake.

Kevin and Su meet up with Hua and share reports of their respective projects. After the meeting concludes and Hua disappears, Kevin stops Su and tells him that the time has come for Project Stigma, a last resort option where humanity must pay a steep cost for, as he deemed all other projects as failures. Su attempts to stop him, but he fails. As Kevin walks away, he remembers the letter Dr. Mei had left him containing Project Regulator – a contingency plan in case Kevin strays from the right path.

Su baits Kevin into the 2nd Divine Key, imploring him to delay the project. Kevin refuses and the two ensues in a fight. Despite being equipped with two divine keys, Su is outmatched in combat and they talk. Su tries to reason with Kevin again, saying that even as pioneers, that they did not have the right to play god and that they should be fighting the Honkai alongside the humans of the current era as equals, but to no avail. Kevin states that he had already found the answer 50,000 years ago, that humanity must defeat the Honkai no matter the cost.

Unbeknownst to Kevin, Su had already activated the first power of the 2nd Divine Key. The world bubble within the key would keep sinking until it reaches the bottom of the Sea of Quanta, inadvertently trapping the two of them, never to return to the real world. Kevin attempts to break the core of the 2nd Divine Key using the Judgment of Shamash’s Zeroth Power in order to stop its sinking, but Su moves into the way of his sword despite knowing that it would cost his life.

Kevin freezes his sword at the last second to save Su and eventually cascades as Honkai beast characteristics start appearing on his body. Before the portal to the world bubble could close, Kevin throws Su out of the 2nd Divine Key, ensuring that Su’s mission would still continue and that he would not be trapped outside of the real world forever. As the portal closes, Su glimpsed at the familiar face of Kevin smiling, reminding him of their high school years and that perhaps, the Kevin of his youth had never left. Su exits the 2nd Divine Key and carries on with his mission, Project Valuka, in search of parallel universes containing crucial information in defeating the Honkai. Before doing so, however, he meets up with Arthur again and teaches him the proper way of using the former’s newly acquired stigmata.

Following the storyline of the 2nd Divine Key manga, Durandal goes through the trials in which she experiences Su’s memories. Durandal claims that Su had lost his footing in the third trial where she had to go through his and Kevin’s fight in the world bubble. She adds that Kevin must have been someone very important to Su, to which he responds by saying that Kevin was his “very best friend.”

Su eventually passes down the 2nd Divine Key as well as a leaf containing important information related to parallel worlds. He tells Durandal that his time was over, and that his physical condition had been declining from the moment he decided to speed up the process of going through parallel worlds. At the end of the manga, he sits back as the world bubble he is in starts disappearing. Leaves of what is presumed to be his memories start to fall and as he passes on to the afterlife, he holds close to his chest a single leaf containing memories of him and Kevin in their youth.

Quotes
"But my abilities matter not, so long as I can find Kevin."

- Su, Chapter 31

Fanon
KevinSu is still a relatively well-known ship in the community despite having comparatively less canon content to go off and is currently the most popular slash pairing in the fandom. Fan content had also risen since the release of the 2nd Divine Key manga, showing more of Kevin and Su’s relationship. Speculation regarding their “friendship” soon increased, especially with moments and/or scenes where Su says goodbye to a portrait of Kevin before going to work during his pre-Fire Moth times, Kevin personally coming to find Su after the 8th Herrscher has been dealt with, the two traveling together for thousands of years seeing the rebirth of human civilization, and many more.

In addition, since the release of Alhaitham in Genshin Impact ver. 3.4, many have noticed the striking similarities of Kevin and Su to Alhaitham (e.g., Alhaitham having a similar hair color to Su, Alhaitham having a build and/or facial expression similar to Kevin, etc). Due to this, Alhaitham can often be seen depicted as their child in fan media featuring the three of them.

Trivia

 * It is implied in Chapter 4 of the Second Key manga that in the 5 years was gone, Su kept a framed photo of his friend at his residence.
 * Although varying from situation to situation, Kevin typically speaks at a much calmer and softer tone to Su, which is shown in Chapter 2 in Elysian Realm.
 * In the Vulgate Cycle, the Lady of the Lake seals an unresisting Merlin, who was in love with her, within a tree, similar to how Su tried to seal Kevin in the Seed of Sumeru where a large tree is present.
 * Amazon UK has stated in a Twitter reply that they ship Kevin and Su.