Su appears as a young man in his 20s. He has very long gray hair and fuchsia eyes with green pupils. He often wears a black polo, golden hoop earrings, a white sash, white boots, a dark gray glove, and loose gray jeans. When Su was still a doctor, he wore a lab coat, a white shirt, and black leggings. During his time at MOTH, he was seen wearing the standard lab coat, white gloves, a black long sleeved polo, and black pants. While he was a high schooler, he had a short haircut and wore a black and white uniform with a yellow tie.
Su was a very calm, serene, wise, kind, and polite man. Unlike his fellow MANTISes, he was not a fighter and wasn't willing to fight unless it was deemed necessary. In his younger years, he was very persistent, stubborn, and selfless.
Su was a doctor at Ninth Hospital for previous 2 years. He'd been working tirelessly to try and cure the Honkai Sickness. On a certain day, Su was assigned to a 10 year old girl named Annie who was infected with Honkai sickness, who he promised to find a cure for. He then was called into a surgery for another patient, which failed, leaving Su feeling terrible. He's then approached by a Mr. Long, a MOTH member, who asks for the patient's body.
He also reminds the agent that he submitted an application to MOTH. Su has a chat with an unknown mentor, telling them about his application, saying he wanted to give it a shot no matter how slim the chances were. After a short talk, the mentor tells Su that he's their best student. Su then considers that, since other survivors of Nagazora were taken by MOTH, that Kevin could be there with them. Su is then called in to operate on that girl. She dies nonetheless. Su is overtaken by grief, but snaps out of it when he says he needs to focus more on his studies.
When Su arrives at the hospital the next day, he sees it blocked off by caution tape. Mr. Long says that the hospital has been quarantined due to a Honkai outbreak. Su tries calling his mentor, but nobody answers. An unknown MOTH agent arrives and tells Su that he can take them to the mentor. The agent briefs Su on what he knows of him, and they comment on how it's impressive that he managed to delay the death of a patient. Su says it's not an accomplishment, as all 52 of his patients have died.
Su arrives at a room within the hospital, where he sees the mentor's body, dead. They had been a victim of the Honkai sickness. The MOTH agent explains that all of the patients with Honkai sickness will be treated at MOTH, and that Su doesn't have to worry about contracting it due to this. Su demands to be allowed to join MOTH, but the agent declines, saying his medical expertise is far too limited to be of any help.
For 2 months Su was tasked to do ordinary hospital stuff, but he would still study every case of Honkai sickness he could find in his off times. When the MOTH agent comes to claim another victim who tested positive for the sickness, he stops in to see how Su's doing. Su hands them a paper on a possible cure for it, but the agent says it won't work. Apparently this is the ninth time he's done so. The agent tells Su to give up on trying, but Su refuses. He asks the agent to continue mentoring him.
When a Honkai outbreak happens in the city a few hours later, Su grabs a girl who'd been attacked by a Honkai beast, and drags them to safety. He notices the Honkai sickness in them, and injects a prototype cure into them. It doesn't work. Su remembers that the agent said that the serum is too weak, and raises the dose of the active ingredient of the serum, and injects it again.
This time, it works--the stripes recede. However, the Honkai beast comes back for it's prey, but Su shields them, getting Honkai sickness from the blow. The agent comes to find Su, impressed by his serum. When a Honkai beast is about to strike the Agent, they call Kevin, and he defeats the beast in one blow. Su is amazed to see his friend again, after over 5 years.
Su passes out, and awakes later in a hospital bed, with no signs of Honkai Sickness. He gets up to have a talk with the agent, and he sees that the child he had just protected died anyway. Su questions how he was cured of Honkai sickness, and the Agent explains that a single dose of the cure can be created from the antibodies found within 1,000 victims. The agent then tells Su that he's made it into MOTH. Su asks about Kevin, and the agent tells him that Kevin is the greatest soldier of MOTH. The agent gives Su a dossier of what Kevin's been doing the last 5 years. He also introduces Su to the concept of Herrschers.
Shortly after Su joined MOTH, the 8th Herrscher arrived. Surviving members of the unknown MOTH agent’s team were placed into what’s called a “Cognitive Cage”, where they were temporarily safe from the Herrscher’s powers. Due to it being temporary, they had to fight back and locate the Herrscher. They did this by putting Su into an "observation hub", where Su was to disengage his cage, go into the 8th Herrscher’s dream, and locate it. Su volunteered to do this mission.
Within the Dream, Su encountered the Herrscher immediately. However, the observation hub was switched off by the Herrscher. Su is caught by the Herrscher, where he’s thrust into yet another dream. He finds himself in a world with the unknown mentor still alive, and Su has cured the Honkai Sickness. Thankfully, the unknown MOTH agent switched back on the observation hub, allowing Su to realize that the dream wasn’t real. They successfully locate the Herrscher due to this. With the ordeal over, Su talks with Kevin, who tells Su that Dr. MEI herself has invited Su to take part in Project STIGMA.
During the battle against the 14th on the moon, Su stayed on Earth, directing things from there. When he learned of the warriors' failure, he told everyone to initiate Project Sanctuary. Upon learning that Kevin is still alive, Su rushed to see Dr. MEI so he could tell her the good news as soon as possible. But he soon notices Honkai Radiation stripes appearing on MEI's neck. MEI tells him that she’s dying of Honkai Sickness, and that the only reason she’s been alive so long is because of Su’s medication.
MEI asked Su to promise to always be by Kevin’s side. Su agreed, saying that Kevin is his best friend as well. She also places Su in charge of Project Regulator, which is a counter-measure in case Kevin strays from the right path. MEI dies before Kevin comes back. Upon seeing her body, Kevin tells Su that it isn’t his fault. When Kevin leaves, Su once again promises MEI to make sure Kevin never strays from the right path. Su enters the cryogenic chambers.
Afterwards, during the Current Era, Su fulfills his promise of staying by Kevin’s side. Many paintings are seen of the two of them together. The next we see of Su, he’s in Britain during the late 5th century. He protects a child, Arthur, from a Honkai beast. The child also confuses Su for a lady, bringing among the legend of the Lady of the Lake. Su joins Kevin and Fu Hua in a meeting, where they discuss all their plans that have failed.
After Hua leaves, Su decides to go back to the 2nd key and carry out Project Valuka. However, Kevin stops him, saying it’s time to activate Project Stigma. Su disagrees, but Kevin won’t listen, and he leaves. Su decides its time to enact Project Regulator.
Su goes outside, and sees the boy once again, who’s being attacked by a villager-turned-Honkai beast. The child has successfully developed a stigmata. Su returns back to see Kevin, who tells Su that he had tested Project Stigma on an entire island. Upon asking Su for results, Su lies and tells Kevin that there weren’t any survivors. Su invites Kevin back to the 2nd key.
Upon him arriving, Su tells Kevin about the Seed of Sumeru—a bubble universe Su had created using the 2nd key, and is unescapable without Su’s assistance. Su begs Kevin to delay Project Stigma. Kevin had realized the trap however, but still came along. Kevin gives Su one chance to stop him, and Su accepts, using the Abyss Flower and the Star of Eden.
The two fight briefly, but Su is defeated easily. Su tells Kevin that he had activated the 1st power of the 2nd key, which means the Seed of Sumeru would sink to the bottom of the Sea of Quanta. Kevin attempts to destroy the key using the 0th power of the Judgement Of Shamash before this happens, but Su blocks him with his own body, which causes Kevin to halt his attack by freezing the Judgement Of Shamash. Kevin, overcome with grief, grabs Su and throws him out of the Seed—back into the real world. He tells Su that he must continue with Project Valuka. He agrees to do so.
When he arrives at the real world, Su finds the boy, who’s name is Arthur, and teaches him how to use his stigma. After doing so, he returns back to the 2nd key to continue his mission.
Su claims that MEI entrusted him to control Project Valuka, which he describes as "To perform a virtual analysis of other worlds." Su says that he's kept vigil for millennia, seeing thousands to millions of worlds that fell to the Honkai, and not a single one that's succeeded in beating it. But he keeps up hope, as there are more leaves that are yet to fall. During his time there, he would go and take a look at Kevin, but he never spoke. As he's taking one of these glances, Su smiles and says that "The one [he's] waited for has come." When the 2nd key was activated, Su talked in Durandal's mind, telling her not to be afraid.
Su welcomes Durandal, and tells her that she's in a bubble world he created with the 2nd key. He calls it the Seed of Sumeru. He says he has no malicious intent, and tells her that he's what's called a Pioneer. He tells her that he's here to protect humanity and to help it defeat the Honkai. He demonstrates the power of the 2nd key to her, and shows her different bubble universes and glimpses of her other lives. He tells Durandal his job, and explains to her that she's the key to defeating the Honkai. When she asks how, he gives a complex summary, and says it'd be easier for her to understand if she just trusted him. When Durandal attempts to break out of the bubble world, Su says that he's foreseen this, and goes behind her and breaks her spear.
He says that since Durandal refused to work with him, he must force her to stay. Due to her distrust, he uses another plan of his- using the 2nd key, Su creates a doppelganger of Durandal, saying that he must extract the quantum power from Durandal and put it into the clone. When Durandal launches herself at him, Su simply grabs her fist, blocking the blow easily.
He lands a strong punch on Durandal, knocking her to the ground. When Durandal summons her King, Su uses the 2nd key to create a circle of Karma, preventing her from attacking him. Su says he's unable to defeat her with his powers, so he calls upon the 2nd key, which takes Durandal away, into a dream-like state.
During her time in the first world, Su comes in and gets rid of Ragna, saying she's one of Durandal's beacons. Su monitors the situation, taking note of how Durandal feels about Otto.
Later, Su is impressed with how Durandal's progressed in the bubble world, saying only beings who could keep their "self" intact could pass the trial of Dharmakaya. However, he has one more trial for her, and he puts her into the trial of Nirmanakaya, as well as giving her “crucial knowledge for the saving of our world.” Su also tells her about the battle against the 14th Herrscher on the moon, as well as the ordeals he’s been through in the past 1500 years.
He puts Durandal into her final trial—the re-enactment of Su vs Kevin. However, instead of fighting Rita (who was the replacement for Kevin), Durandal joins her—asking to assist her. While Su is contemplating this, Durandal awakes, and hits Su. The two talk, and Durandal tells him that the Current Era has the right to decide their own path, and Su agrees, and gives Durandal the 2nd key, as well as a battlesuit, which was the Seed of Sumeru.
He tells her it will help control the bubble world inside of her. He says that, with the seed having been given to her, he will sink to the bottom of the sea of quanta. He tells her that he’s been overworking himself, speeding up the process of his observation, and it’s taken a toll on him. He also gives her a leaf which contains the important info of parallel universes he’s observed.
With Durandal gone, he takes one final look at Kevin, as well as grabbing a leaf which shows them together in High School. He says that he’ll “Look for the answer to that question in the afterlife, if there even is one at all...”
Afterwards, Su promptly finds himself in a void, saying “This place... it does exist...”. A disembodied voice says that it “Applauds [Su] for finding this place. [Su] seek the universal truth that governs the Honkai itself.” It says it hasn’t met a human in eons, and that it’s bored. It challenges Su to some sort of board game, saying that if he wins, the entity will give Su the answer.
- Su, like his fellow MANTIS and former comrade Fu Hua, is often mistaken as a person of the opposite sex due to his soft features and long hair.
- Su uses many words in Sanskrit to describe his trials and bubble world. He often talks about things that are most likely Buddhist. This implies he may believe in that faith.
- Su's Active Honkai Reaction form has the form of a peacock.
- In the manga London Holiday, Kevin Kaslana is referred to as Merlin, while in Second Key, Su is referred to as the Lady of the Lake. This connection is deeper than expected due to many similarities.
- In a version of Vulgate Merlin, Merlin teaches the Lady of the Lake all of his secrets and she seals him into a tree. Su does a similar act by staying with Kevin Kaslana and later, sealing him into the Sea Of Quanta in his personal bubble world (that happens to have a tree).
- In another version of The Legend Of King Arthur, the Lady of the Lake and Merlin are lovers. Although Su and Kevin are close, they aren't in a romantic relationship. Some of the community still likes to ship them with each other though.
- Like the Lady of the Lake, Su helps a boy named Arthur control his newfound power. In Second Key, it is his Stigmata, but in The Legend Of King Arthur it is his sword.
- In London Holiday, Kevin Kaslana is implied to be Merlin. However, this was contradicted in Second Key, which shows that Su seals Kevin when Arthur is still a child. Meaning it was most likely retconned.
- Su used to go out for drinks with his late MOTH mentor. He quit after Kevin told him that drinking was bad for him.
- According to Su, he would have to take a look at 32,874 unique bubble universes in order to find the universe that defeats the Honkai.
- Su owned 3 Divine Keys before he sealed Kevin Kaslana into the Sea Of Quanta: Abyss Flower, one of the Twins of Eden, and Cosmic Juggernaut.
- The bubble universe Su created with the 2nd key, the Seed of Sumeru, has the same name as a region of Genshin Impact's Teyvat.
- Sumeru is a nation of rainforests and forests, biomes that have many trees. While the Seed of Sumeru is known for having a huge tree.
- The current Dendro Archon of Sumeru is known as the God Of Wisdom. Su also seems to be very wise as well despite not being a god.
- The three known MANTIS Previous Era survivors Fu Hua, Kevin Kaslana, and Su, are all older than Morax, the oldest archon of Teyvat, by several thousand years. Morax is over 6000 years old while the MANTISes are over 50,000 years old.
- Su has been observing other worlds using the 2nd key for 4500 years, a detail that was only shown on the Chinese version of Second Key.
- In Chapter 8 of St. Freya High, it was said Honkai beasts were spotted in 2717 BCE of the Current Era. Meaning that the MANTISes came out of their cryogenic pods sometime before that.
|Characters||Kevin Kaslana • Elysia • Aponia • Eden • Vill-V • Kalpas • Su • SAKURA • Kosma • Mobius • Griseo • Fu Hua • Pardofelis|
|Recollections||Hero's Memory • Pristine Memory • Ascetic's Memory • Singer's Memory • Fool's Memory • Mad King's Memory • Buddha's Memory • Sakura's Memory • Youth's Memory • Serpent Master's Memory • Painter's Memory • Soldier's Memory • Mortal's Memory|
|Sigils||Remembrance Sigils (ER)|
Sirin • Fu Hua • Dark Hua • Void Archives • Sora • Siegfried Kaslana • Kiana Kaslana • Ana Schariac • Benares • Yuna • Avrora • Agata • Galina • Wendy • Pepper Mint • Lin Zhaoyu • Yan Shiluo • Kallen Kaslana • Yae Sakura • Yae Rin • Ji Xuanyuan • Fuxi • Nuwa • Shennong • Su • SAKURA • Veliona • Final Herrscher • RIN • HIMEKO • 8th Herrscher (Previous Era)