Note on naming: All names are constructed in the Chinese fashion of: surname （姓） + birth name （名） - courtesy name (if any) （字） - title (if any) （号）.
Chang Geng (长庚) / Li Min (李旻)
Voiced by: Yang Tianxiang (audio drama)
Played by: Chen Zheyuan (live-action, adult), Xiao Tianren (live-action, teenager), Qi Chengjin (live-action, child)
Click here to see Chang Geng when he was younger
- Afraid of Blood: Subverted; he doesn't have a phobia of blood. However, he cannot stand the sight of seeing Gu Yun bleed in any way.
- Because You Were Nice to Me: The main reason he fell for Gu Yun. While Gu Yun is found wanting as a father figure, as a person he was unconditionally kind to Chang Geng.
- Beware the Nice Ones
- Casual Kink: While he and Gu Yun gradually stop seeing each other as parent and child, respectively, there are hints that Chang Geng takes special pleasure in calling Gu Yun "father" during their more intimate moments.
- Child by Rape: For a long time, he thought he was this and that it was why his mother hated him and repeatedly attempted to kill him. Eventually, it's revealed that this isn't the case, and the truth is much, much more complicated.
- Covered in Scars: His abuse at Xu Niang's hands left his body riddled with scars.
- Dark and Troubled Past: A huge part of his childhood involved his mother trying to kill him in different ways. And that's before he learns that his mother isn't actually his real mother.
- Easily Forgiven: Deconstructed. While Liao Ran mourns his mentor's death, he doesn't resent Chang Geng for killing Liao Chi since he knew it had to be done.
- Gentleman Snarker: Chang Geng is capable of being bitingly sarcastic while remaining composed and polite.
- Good Is Not Soft: He does the very best he can to protect Gu Yun and in turn, Great Liang. But that means he is more than willing to use ruthless means to root out and eliminate any obstacle once and for all.
- The Good King: After succeeding his half-brother, he proves to be several times more capable than Li Feng in running the country.
- Hates Being Alone: Some of his nightmares tend to be centered around his fears of Gu Yun abandoning him.
- He Is All Grown Up: In the instances when he and Gu Yun haven't seen each other for years before meeting again, Gu Yun's first reaction is to think of the trope word for word.
- I Want My Beloved to Be Happy: He's hopelessly head over heels for Gu Yun, but he tells Gu Yun that he will not make a move on him and will do his best to let go of his love if Gu Yun doesn't reciprocate his feelings. Thankfully, that doesn't happen.
- Like a Son to Me: At the start of the story, Gu Yun saw Chang Geng as a son and planned to raise him as his own once the truth about his lineage comes out. Likewise, Chang Geng also sees Gu Yun as a father, except that their quasi-familial relationship conflicts with his growing feelings for Gu Yun.
- Lost Orphaned Royalty: Chang Geng is revealed to be a prince; his biological mother died giving birth to him, his stepfather gets Killed Offscreen early in the story and his stepmother commits suicide, and his biological father passes away shortly after.
- Meaningful Name
- The Medic: In the years that he and Gu Yun haven't seen each other, Chang Geng studied medicine under Chen Qingxu's guidance in the hopes that he could cure Gu Yun's illness as well as curb the adverse effects of the Bone of Impurity.
- Muscles Are Meaningless: At fourteen years old, Chang Geng could already wield a sword that's at least thirty kilograms heavy. If what Chen Qingxu says is any indication, this has something to do with the Bone of Impurity, which essentially grants a person with the strength of two people.
- Royals Who Actually Do Something
- Single-Target Sexuality: It becomes obvious that Gu Yun is the only one Chang Geng would feel any romantic, let alone sexual, love for.
- Supreme Chef: Chang Geng knows how to make a damn good bowl of longevity noodles.
- Warrior Prince: Although he doesn't usually get to fight in the battlefield, he has more than decent combat skill, which he can put to use if needed.
- Was It All a Lie?: He learned in one night that everything about his life is not all it seemed, including the fact that the man he looked up to as a father is actually a war general. Needless to say, he wasn't happy about it. Although it doesn't take more than a sincere apology and some reassurance from Gu Yun for Chang Geng to immediately forgive him.
- When You Coming Home, Dad?: Some time after he's officially adopted by Gu Yun, he's often left in the house while Gu Yun spends a long time away handling military matters, much to Chang Geng's dismay.
- Wise Beyond Their Years: Given that his mother did a piss-poor job of raising him (which is only putting it lightly), Chang Geng essentially took care of himself during his childhood and thus was more mature than most people his age.
- Would Hurt a Child: Implied in Li Feng's final moments, since Li Feng fears what could happen to his son if he refuses to give Chang Geng the throne; although Chang Geng could have just been bluffing.
Gu Yun (顾昀) - Zixi (子熹)
Voiced by: Zhang Jie note (audio drama - adult), Qin Se (audio drama - child)
Played by: Tan Jianci (live-action, adult), Shiyue Anxin (live-action, teenager)
The Marquis of Order and the leader of the Black Iron Battalion.
- The Ace: One has to be an extremely skilled fighter to lead the entire Black Iron Battalion.
- Berserk Button: He doesn't really take kindly to monks, because one previously told him that he would bring nothing but bad luck. When he learned that Chang Geng was (willingly) spending time with Liao Ran, his response is to put out a warrant of arrest for the latter. Then when Chang Geng later expressed his intentions to travel the world with Liao Ran, Gu Yun is so incensed that he immediately rejects his request.
- Brutal Honesty: He's not afraid of voicing his thoughts, even if they might offend someone. He can be tactful if necessary, however.
- Corporal Punishment: It only happens once, but he inflicts this on Chang Geng when the latter verbally castigates himself after suffering another painful episode from the Bone of Impurity.
- Crazy Jealous Guy: He's not really one, but there's one instance when he stole the flute that Chang Geng gave to a young girl. Other than that though, he knows that Chang Geng has eyes only for him, so he doesn't have to worry.
- Deadpan Snarker: He has quite the smart mouth and the acidic tongue.
- Deuteragonist
- Determinator
- Dreadful Musician: He can't play a flute to save a life. This is justified by his partial deafness, but even with practice he's incapable of improving even a bit. His playing is even considered a Brown Note in-universe, scaring anyone within earshot to almost literally run for the hills.He was now even better at urging people to urinate than before. A short burst of a foreign folk tune destroyed people's hearts. Not far away, a horse waiting for its hoof to be fixed was frightened as if surrounded by a group of wild wolves, letting out a whine like it was in pain. Meanwhile, a patrolling Black Eagle landed from the sky with unsteady footsteps, stumbled and directly fell to the ground, appearing in the posture of begging for New Year's money.
- A Father to His Men: There's no doubt that he's a great military leader who always acts for the good of his country, and all soldiers of the Black Iron Battalion respect him because of this.
- Handicapped Badass: Both his sight and his hearing are impaired. This didn't stop him from becoming the Marquis of Order.
- High-Class Glass: He wears a monocle.
- Image Song: "The Moon Resembling a Stream of Gold", the ending theme song of the audio drama, counts as one for Gu Yun as it's sung from his point of view. Not to mention, it's Gu Yun's voice actor who's singing the lyrics.
- Improbable Aiming Skills: Even when his sight is compromised, he's still good with an arrow.
- Jerk with a Heart of Gold: He can be lacking in social graces and is also sharp-tongued, but Gu Yun watches out for his men and fights for the safety and welfare of his country. And there's how he cared for Chang Geng.
- Obfuscating Disability: After Gu Yun is revealed to be the Marquis of Order, Chang Geng thought that he was just faking the partial deafness and blindness as part of his cover. He wasn't.
- Parents as People: He sincerely tries to be a good father to Chang Geng, but due to his lack of experience as one (coupled with some personal issues that left him emotionally stunted), there are times when he struggles in giving Chang Geng the support he needs. Chang Geng does acknowledge that Gu Yun may not be the perfect father figure, but he tried his best to be a good one still.
- Parental Substitute: He's something of a father figure to Chang Geng, despite being only around eight years older. Chang Geng even refers to him as yifu, a term one uses in China to refer to their adoptive father. He's then officially appointed as Chang Geng's foster father by the late emperor Yuan He.
- Pretty Boy: He's acknowledged In-Universe to be incredibly good-looking.
- Proud Beauty: He's not narcissistic, but he's not ashamed of acknowledging his good looks. He even calls himself the "Northwest Flower" because he considers himself the most beautiful person in the northwest of Great Liang.
- Scars Are Forever: He has a couple of battle scars across his torso.
- Screw the Rules, I'm Doing What's Right!: He's forever loyal to his country first and the kingdom second, no matter what threats will be thrown at him.
- Selective Obliviousness: Chang Geng notices that he takes advantage of his impaired hearing to pretend that he didn't hear something that he doesn't like or agree with.
- Shipper on Deck: There's no doubt that he's rooting for the day when Shen Yi finally gets to properly court Chen Qingxu without fumbling once.
- Thermal Dissonance: Even in the months of harsh cold, Gu Yun never wears winter clothes in the capital.
- Training from Hell: His father was nothing short of harsh in his combat training. As Gu Yun had said to Chang Geng, his father would beat him with a stick whenever he would mention how he was afraid.
- Vitriolic Best Buds: With Shen Yi.
- Worf Had the Flu: This trope comes into play whenever Gu Yun is in a tight situation where his handicap comes back and he doesn't have his medicine.
- Young and in Charge: He led the Black Iron Battalion since he was a teenager.
Shen Yi (沈易) - Jiping (季平)
Voiced by: Guo Haoran (audio drama)
Played by: Li Hongyi (live-action)
- Affectionate Nickname: Played with; Gu Yun tends to call Shen Yi "old maid" whenever he's snarking at him, but no matter what the two are always on friendly terms.
- Beleaguered Assistant: It's difficult to keep count of the times Shen Yi got exasperated with Gu Yun in some way.
- Cannot Spit It Out: He gets very flustered and nervous whenever he tries to express his affections to Chen Qingxu.
- The Confidant: He's someone Gu Yun can be completely honest with about politics and war, or taking care of Chang Geng. In turn, Shen Yi gives Gu Yun meaningful advice about both.
- Deadpan Snarker: When he's dealing with someone like Gu Yun on a nearly daily basis, he's bound to be this.
- Hyper-Awareness: For some reason, Shen Yi can already surmise that Chang Geng and Gu Yun have done it just from one look at them both.
- The Lancer: To Gu Yun.
- Like an Old Married Couple: Shen Yi and Gu Yun are friends and friends only, make no mistake of that. Yet the way they bicker — which happens rather often — is very much reminiscent of a couple arguing over various small things.
- The Medic: Downplayed. He's not a doctor, but when there's no doctor nearby he's in charge of cooking up the medicine that temporarily suppresses Gu Yun's sensory deficiencies.
- Mr. Exposition: He occasionally serves this role in the audio drama.
- Mythology Gag: Although it could also be coincidental, Shen Yi's family name might be a reference to the character Shen Wei from Priest's earlier novel Zhen Hun, since it's written with the same character "沈".
- Nice Guy: While he's a bit snarky, overall Shen Yi is a man with a good heart.
- Number Two: He is Gu Yun's second-in-command, although he introduces himself as just one of the many soldiers of the Black Iron Battalion.
- O.O.C. Is Serious Business: In the later parts of the novel, Gu Yun notices that Shen Yi is acting odd since he seems to want to stick around at Gu Yun's house and appears reluctant about leaving. He eventually learns that it's because Shen Yi's father has prepared an Arranged Marriage for him, which Shen Yi is trying to avoid by not going back home.
- Ship Tease: It becomes obvious that he has feelings for Chen Qingxu.
- Squee: It's low-key, but he gets curious and excited when he sees new innovations in machinery. Gu Yun even joked to Ge Banxiao that if he showed his engineering knowledge to Shen Yi, the latter would ask for his hand in marriage. And then there's how Shen Yi geeks out and coos over the wooden bird...
- Third Wheel: Given that he's Gu Yun's closest friend, he tends to be this to Gu Yun and Chang Geng, albeit unintentionally.
- Undying Loyalty: He may be complaining often about how Gu Yun can be a handful to deal with, but Shen Yi won't hesitate to ride to the underworld with him.
- Vitriolic Best Buds: With Gu Yun. He may often get exasperated with him and they bicker to no end, but that's a testament to how their friendship extends beyond the professional relationship between general and lieutenant.
Li Feng (李丰) - Long An (隆安)
Voiced by: Wei Chao (audio drama)
Played by: Sheng Yinghao (live-action)
- Character Death: He dies in the final chapters of the novel.
- The Emperor
- Fatal Flaw: His paranoia. While it isn't without reason, he counts everyone as an enemy, and by the time he's used up what little luck he has, it comes to bite him in the ass.
- Obstructive Bureaucrat: He becomes the next emperor of Great Liang; and while he isn't the Big Bad, there's a lot of friction between him and the protagonists because of the plenty disagreements they have about how to handle the nation and its people. And Li Feng is an extremely paranoid man.
- Papa Wolf: Li Feng genuinely loves his son and dreads the thought of anything happening to him, which is why he chooses to make Chang Geng his successor in his final moments since he doesn't want to burden his young son with the dangerous responsibilities of his position as Emperor. That, and Chang Geng may or may not have insinuated that harm may come to Li Xiang if Li Feng does not give him the crown.
- Properly Paranoid: He's mostly correct that there are traitors hiding and plotting both in and out his court. The problem is that he counts Gu Yun and Chang Geng among them.
Chen Qingxu (陈轻絮)
Voiced by: Long Shisan (audio drama)
Played by: Sun Anke (live-action)
- The Medic: She is a doctor after all.
- The Mentor: While she considers herself only a half-teacher to Chang Geng, she still taught him many things about medicine.
- Ship Tease: Shen Yi clearly has a crush on her, and the later chapters hint that his affections aren't unrequited.
- The Stoic: Downplayed; she's not an Emotionless Girl, but she's normally composed and unflappable.
Cao Niangzi (曹娘子) - Chunhua (春花)
Voiced by: Su Shangqing (audio drama)
Played by: Song Jiyang (live-action, adult), Kong Xiangfu (live-action, teenager)
- Attractive Bent-Gender: Once he dons the proper get-up, he's completely convincing as a woman.
- Cunning Linguist: He's able to pick up on the basics of the Japanese language just from a few days of listening to two Japanese men talk to each other.
- Meaningful Name: Niangzi is Mandarin for either "lady" or "woman", and Cao Niangzi, while born male, likes to dress up as a girl.
- Raised as the Opposite Gender: He's born a boy, but he was raised as a girl by his parents to counter bad luck. Not that he minds.
Ge Banxiao (葛胖小) - Chen (晨)
Voiced by: Xing Chao (audio drama)
Played by: Dong Yanlei (live-action, adult), Gao Yuyang (live-action, teenager)
- Gadgeteer Genius: His father was a blacksmith, and Ge Banxiao has learned a thing or two from him, eventually growing up to become a skilled mechanic and engineer.
- Meaningful Name: Ban and Xiao translates to "fat" and "little", respectively, which accurately describes Ge Banxiao's figure.
- Naked People Are Funny
- Nice Guy
Liao Ran (了然)
Voiced by: Jin Xian (audio drama)
Played by: Yu Chengen (live-action)
A monk of the Hu Guo Temple.
- O.O.C. Is Serious Business: Because of his oath of silence, when he breaks out in tears and sobs out loud, it means something serious happened. And something did: halfway through the novel, Liao Ran realized that his mentor is a spy working for the foreigners. He cries again after Chang Geng kills his mentor.
- The Pig-Pen: While he doesn't look like it, he's not fond of bathing and he's observed to have never washed his robes at least once. Chang Geng and Gu Yun are predictably (and understandably) grossed out by this.
- Pretty Boy: Gu Yun, a Proud Beauty himself, admits that Liao Ran is rather handsome. Even Cao Niangzi gushes over how beautiful Liao Ran is.
- The Speechless: He took a vow of silence, so he communicates only via writing or sign language.
