Demiromantic and aromantic coded characters

• Takahashi Satoru seems to be both asexual and aromantic. 
  • He is angsty and a bit of a hermit, and is a bit guarded. 
  • He is also blunt.
• At one point one of the characters go to an ace/aro meetup

One of the FLs very clearly explains that she is aromantic and has no interested in romantic relationships

• Haru Tsugumi is not interested in dating people and considers herself asexual. She's likely also aromantic.
  • Blunt type.

• In the last episode, Kunou says he has never liked men or women, but he was once interested in a guy. I would take this to mean he is probably demi/gray romantic, closer to the aro side. If even that! He has  a very high wall to pass for just being friends with him, so his attraction to Garo might not even be romantic. It's not that he is particularly guarded, but more that he just isn't super interested in having friends and is pretty comfortable with that.
  
  • eccentric and logic driven
  • cool headed

• Fujusaki Nozomi is not interested in dating or marriage. 
  • Generally a warm person.

• Takasugi Ume defines herself as asexual, but also seems to have no interest in romance. 
  • She is eccentric and open-minded. 
  • Blunt as well.
• Matsuda Ken's ideal relationship is with someone who has a certain amount of emotional distance. He tends to use romance at a tool to  have sex, and doesn't seem to have any genuine interest in romance. (I will note that in season 3, his ex-girlfriend says they're in love with each other. While I think he really cares about her and they're super compatable, I personally wouldn't read Matsuda as in love with her, though I can see why others would. Also, I do not recall him ever confirming her assumptions about his feelings.) 
  • He is the cool playboy type.
• A-Kun seems to view relationships as a way to blend in with society while pursuing his sexual desires elsewhere. We don't see much of his fiancé though, so we can't fully know the nature of their relationship. I would guess he is aromantic though. 
  • He is the cool playboy type with an eccentric vibe.

• The story is about a girl who doesn't understand why everyone cares so much about falling in love! It's really frustrating to her that people care so much about her being single. She thinks there are other things in life to focus on instead, hobbies and interests and friendships for example.

• He seems to have zero interest in dating or sex. When everyone expects him to end up with the female lead, he instead respects her as a friend. Other characters try to imply that the two might have something going on, and the female lead occasionally seems intrigued in a tsundere sort of way, but he has zero interest. 
  • He is eccentric and blunt.

• Kui Yoshiaki seems to be only sexually interested in others. He does have one regular sexual partner, but it doesn't seem to be associated with any romantic implications as far as I can tell. 
  • Eccentric playboy.

• In episode 5, Jinnai Kazuhisa says something like "is liking people fun?" which made me wonder if he's being coded as aromantic. 
  • Badboy

• Majima Makoto seems to date only because it's expected of him and not because he's genuinely interested in pursuing a romantic relationship. 
  • He is the kind-hearted hero type with a rough edge
  • Badboy

Idk why I didn't catch this, but Kotora might be aromantic? He seems to have no interest in romance, though he does have an interest in sex

• Eccentric
• Hot-headed

• Minagawa Nanami doesn't seem to actually be romantically attracted to her husband. She kind of got married because she figured she was supposed to. She enjoys his company, but she doesn't seem to have a lot of love for him. In addition, when she later has a different romantic prospect, she seems to consider this person as a very close friend instead even when they're romantically paired with each other. 
  • Airheaded and hermit-type

• Master has no interest in romantic or sexual relationships. His past is a mystery, so it's possible he could have had a romantic past (and I haven't watched the rest of the series so correct me if I'm wrong). 
  • Cool and mysterious

Some people interpret some side characters as aromantic or asexual because they don't show interest in anyone. I can understand why (especially since many of these characters don't marry in adulthood), but I could also understand if someone did not interpret these characters in this way (mainly because additional romances would be too much plot-wise, and doesn't really fit the tone of the show).

• idk how to explain but Iwaya Sumire gives off gray romantic vibes. Maybe because she can strictly differentiate between affection and romance, and doesn't really fall for others when we would expect her to. 
  • Cold and blunt type.
  • Logic driven.

• Rohan is possibly aroace? He seems to take no interest in anyone. 
  • Eccentric and cold.

• Jang Bong Hwan doesn't seem to have a romantic interest in people for the most part. He has flings and clearly has sexual interests in others, but his romantic interests in people form much slower. Because of this, I think he might be demiromantic or gray romantic.
  • Badboy
  • Playboy

Thanks to Tristram for these notes! Check out their list for more demi characters

• "The ML reads to me as being on the ace spectrum, because he's perfectly happy in a relationship with the FL that includes cuddling while sleeping, but no sex or kissing. It doesn't seem to occur to him that she might be unhappy with this arrangement.  (They do kiss at the end, but sex is never addressed.)"
  • Awkward
  • Eccentric
• These two seemed kind of like the platonic version of sex friends from what I remember. One could argue that cuddling and stuff is romantic, but I think there's also room for interpretation that he is simply not oriented towards romantic attraction and just enjoys skinship with the FL. I'd have to rewatch it to say for sure though.

• Ida is confused about how attraction works and is possibly demiromantic or grayromantic of some kind. 
  • He is a cool-headed himbo with an awkward vibe.

• Sangwoo does not get the hype around romance at all. Most likely some kind of grayromantic. 
  • He is the rude, blunt hermit type.
  • Sees the world through logic.

• It's been a while since I watched this one, but Suho has zero interest in dating and considers it a waste of time (similar to Semantic Error). 
  • He is the cold and blunt type. 
  • Logic focused.

This gives off the vibe of being a metaphor for demiromanticism. Basically any show that uses the trope where someone can't experience love gets on this list for me. 

• Zhu Xuan Ji has some sort of anti-love magic on her and it's only through developing a strong and deep bond with her co-lead that she can finally fall in love. 
  • She is a bit airheaded and sheltered.

This could also be interperted as being a metaphor for demiromanticism, but I don't think it's a strong contender.

• Dongfang Qing Cang has cut himself off emotionally in order to develop a strong asura fire. He is forced to get to know her in order to protect himself, and then falls for her. I don't think he really fits on this list because it seems to be implied that he catches feelings for her pretty early. However, there are also a lot of excuses for these acts of affection, and these excuses take out the romantic meaning from his character. Because of this, I think it's possible to interpret Dongfang Qing Cang as demiromantic (though this is likely not the intention). 
  • Rough and cold personality.

• Yutaro hires someone to be his girlfriend, but not because he wants to date her. Instead it's because he wants to learn how to use makeup. He doesn't seem to have interest in actually dating anyone at all. 
  • Sweetheart type.

• Choi Sang Eun doesn't easily fall for others, and she also seems to have only fallen for someone when she reached her 30s. She is possibly demiromantic. Her romantic interest in the lead doesn't start until about five years into their dynamic.
  
  • Warm type.
  • Cool-headed

• The ML is 29 when he first experiences romantic attraction, though he has dated people in the past. He even goes so far as to wonder if he's never truly loved his exs.
  
  • Warm

• The FL has a flashback to childhood where her friends ask her who she has a crush on. She doesn't seem to reply. We get a sense she hasn't really had a romantic interest in other people for much of her life, though she seems to now.
  • warm...? she's like warm in an introverted way, as in, she's warm but only with people she likes

• One of the FLs asks the other if she likes guys/gals and she's like, "I'm not really sure" or something like that. Not really sure if she counts as demi or not, but she qualifies for this list.
  • insecure

• In episode 7 Woo Jae says he has never been in a romantic relationship and that he doesn't want one either. He does end up in a romantic relationship (as they often do in kdramas) but I personally wouldn't interpret this differently. It's possible he's demiromantic, but I think its also possible he found someone he was willing to be in a relationship with even if he could not experience love. They were just very compatible people in a lot of ways.
  
  • Playboy
  • Coolheaded
  • Warm/affectionate

• Athena pointed out that Joanna is likely aromantic. She seeks out sexual relationships, but is not interested in romantic ones.

• Momoi Miori seems to be aromantic. She has zero interest in romance, but she is interested in sexual relationships. the open ending seems to imply she should change to be more romantiic, and the ending dialogue seems to suggest that she does have romantic attraction but that she separates it from sex? Not too sure about this one.
  
  • cool-headed
  • confident

*spoilers*

Headcanon but Ayane-chan reads very heavily as aromantic. There are some hints throughout, but the most obvious is in episode 10 when she's explaining that despite being with her boyfriend for x amount of time, she hasn't fallen in love with him, and that this has been a problem in previous relationships as well. BUT by the 11th episode it turns out she has a crush on her teacher so who knows. Gray romantic? demiromantic? Not sure but it's enough for this list.

• Cool-headed
• Damaged baggage
• Kind

StarryNights noticed the following about Akira and headcannons him as demiromantic:

• it's mentioned by Akira's friends that he's never talked about or been interested in talks about crushes before
• didn't show romantic or sexual interest in Yuuki until after getting to know him on an emotional level (because of this I would also headcanon him as demisexual)
  
  

Well I'm not sure if this counts. Chihiro says she loved someone once(?) but it was like bad for her? She describes it like being sick, like an allergy. And she says she doesn't really need love to live a happy life, but she thinks sex is like something she needs to live. Regardless, whether it's intentional or not, this is some decent dialogue on differences between romantic and sexual attraction.

• Eccentrric
• Cool-headed

demiromantic ML (head canon). He says he has not fallen in love and doesn't expect he will, or something along those lines. As is the trope, he does eventually fall in love. 

• bratty
• heart of gold

Naruse in episode 4 says he envies everyone else because he can't seem to like others the way everyone else does. He may experience sexual attraction to others though based on his implied sexual flings, but we don't actually see him experience attraction (just the messy breakups) for most of his storyline. He does eventually fall for someone so maybe more accurately he's some sort of gray-romantic.

• Bratty
• Playboy vibe
• Arrogant
• Hot-tempered
• Cold hearted

In the first episode, the ML says he's never been in love and can't relate to the experience of confessing to someone. Seeing at this is a BL though I'm probably going to end up considering him gray or demiromantic based on the usual trends. 

As noted in the comments of this list by King Julian, there is an aroace character. I have not finished watching this show so I have no comments on this.

As noted by Athena. I have not watched this yet so no comments from me.

 Athena  noted Champ was aromantic. I have not watched it.