Yoora (Yuro) Odette - Yuro, full name Yoora is a seemingly fragile, sweet and timid girl. She was a sheltered and isolated girl who sought out meaningful companionship. She undergoes a lot of experiments and traumas along side a girl she meets, named Keiro which changes her permanently. She wants love and relationships that hold irreplaceable bonds, and irreplaceable memories. She tries her best to be nice to the people around her, as she knows how it feels suffer the opposite. She felt like a shape shifter, molding to other peoples wants and needs. This often leaves her feeling strange and empty. Fortunately or unfortunately she experiences one of the biggest changes in her life after she get enrolled in Heaven's Institute, gets selected for several experiments and meets a variety of new people to connect with (Yuro's Symphony Story). Post Yuro's Symphony Yuro is different, she knows who she is, and experienced so much pain, has grown so much and learned so much knowledge about her and the world. Her and Keiro are inseparable, truly bonded, and likely in love. Whilst the experiences haven't 'hardened' Yuro, she has a different perspective on life, and whilst being more happy and fulfilled- values her mortal human life less and less. Doing more dangerous things, daring things, then stitching herself back up to do it again, joyfully. She wants to explore the world, she never wants to be trapped again. Yuro is close with Keiro, Ruina, and Maja.
fact - yuro likes quiet, keiro, physical sensations, black turtlenecks and comfort, the wind in her hair, looking at orchids and picking wildflowers. cats cradle and convenience stores. dislikes unnecessary pain, and being startled.

Keiro Belikova - Keiro is a fatigued, exasperated, and sometimes blunt girl. She has tired eyes, and a rigid boney exterior. She is often seen as an older sister to other girls despite her not necessarily having her life or self together. She struggles with vices, and having a short temper. She is always trying to look after those around her and tries her best to protect them. In Keiro's perspective she has never been much of a little girl, she's always trying to take charge of situations and keep herself safe, because she had to. She used to go about it the wrong way, but she's redeemed herself according to many around her (students at Heaven's Institute). At school was mostly alone except for being with Maja and sometimes Ruina. Her approaches can be unconventional, and she can be neurotic with those she cares about. She struggles with self-doubt and insecurities regarding if people truly love her. Keiro is very harsh with those she deems unfit or to not be good people, but to her that is what is right to do. She is wanting to find her purpose, she doesn't want to just float around confused. She will research day and night to find out what is going on and why she is there, and she's getting closer to it each and every day. Post Yuro's Symphony Keiro thinks she has found her purpose and part of it has become Yuro, being with Yuro, protecting her, living life together. Keiro forms strong bonds and feels utterly connected and intertwined with her. Keiro is close with Yuro, Maja, and Ruina.
fact - likes black and red, loving yuro, smoking on benches with maja, pitch black nights, bleeding, restraints, winning.

Ruina (Rui) Marcellaine - Ruina also known as Rui, is bubbly, a bit awkward and often manic. I like to describe her as 'derpy' but she is also slightly demented. Ruina has a fascination with old medical procedures, technologies, and Doctors- which is something she has in common with Astrid. She enjoys researching and feeling accomplished by what she finds, along with documenting it all. She likes meeting new people, and teasing people that aren't her own size (much bigger than her). She loves to make those around her laugh and be happy; despite having many friends and being widely loved, she can be very nervous or skittish. She can be annoying or get called too loud around her peers. Ruina just wants her loved ones to know she cares about them, and would do anything for them. So, she tries her best to be good, as she wants them to stay forever. Ruina has been abandoned and hurt before by someone she cared about deeply, so she has a complex about people not staying. Love is one of the most important things to Ruina, and she will do anything to protect it. When Ruina was going to the Heaven's Institute she used to walk near the run down clubs and strange shops in the 02 district, exploring the dilapidated buildings.
fact - likes eating sweet food, colourful hair, cigarette burns, being happy, maja, doctors, being wounded and patched up again. dislikes conflict, awkward situations, or feeling claustrophobic.

Maja Magdalena- Maja is reserved, independent and can be perceived as quiet. She is a ghostly figure, moves like she is levitating half an inch off the ground and has soft gentle footsteps. She enjoys being alone, working on the things that give her meaning. She feels dedicated to her scholarly endeavours and her art. She's devoted herself to her passions; art, math and the harp. Those three things is why she is living. She does not care how she's perceived by those around her, and she practically lives in her own world. She doesn't not care much about anything other than her little world and her very small group of loved ones. She doesn't feel a lot of pressure to keep up with too many friends, she's indifferent to the concept. As long as she has one or two people to care for, that's enough for her. Those people are currently Keiro and Ruina. Maja is working on something within herself, and she is also looking for answers. In the simulated world, she is intertwined with a 'wolf'. Their relation, and connection is slightly unclear.
fact - Maja has a mental disorder which causes her to feel repulsed by many foods, and she often eats things that aren't considered food- such as flowers from her room, her diet mainly is consisting of meat, flowers, white pastries, and milk. likes wearing her glasses, reading outside, and causing trouble. dislikes bombastic people, crassness, and unplanned hangouts.

Yuro, Keiro, Ruina, and Maja were all students at the Heaven's Institute, a prestigious all girls school. They find each other in an unexpected spot at HEARTKNOT, the simulated world by HKRE; with no past memories to help them understand the world they've been brought into.

Ophelia Dupont - Ophelia is a tender and motherly girl. She knows how painful it can be to have no one being kind to her, so she never wants anyone to feel that way. She has big wet eyes, a soft smile and a warm core. She likes order, patterns, and routine. Listening to music on record players, and eating beautiful meals with Serenity and Aito. She is the diplomatic head of 3HEART and the voicebox of HEARTKNOT. Despite being the head girl, she is quite understanding. She doesn't enjoy how harsh the things she is involved with can be.. but she admires the strength and support they provide to so many. She is constantly seeking a parental or domineering figure she can turn to during the stress of managing students and parenting so many girls around her. Many rely on her because she is so compassionate; although a small minority of the girls call her strict because she takes what authority says and enforces it heavily, but they know Ophelia only wants the best for them.
In HEARTKNOT, Ophelia's true love is HEART. In HKRE, Ophelia still feels similarly, she 'knows' that HEARTKNOT is a simulation, but is always eager to join those experiments and appear there. It is her devotion and a concept she struggles to shake. She loves the simulated world more than her "real" world, and the lines between the two start to blend. The real is just a countdown until she can retreat back to HEARTKNOT and speak with it. Ophelia was a student at Heaven's Institute at the same time as Aito, Serenity, (and like her older sister Evette); and underwent an experiment of a simulated world similar to HEARTKNOT. She was strong enough for the 01 foundation to want to pull her from the experiment and hire her at the facility. However as time passes, Ophelia grows more and more dependent on the escape to HEARTKNOT. Ophelia is close friends with Serenity, and Aito. She is getting closer with Keiro and Yuro. She is acquaintances with and loved by many.
fact - ophelia wants someone to take care of her, loves pigtails and changing her hair, and photography / visual expression. she wants to be held tenderly and shown the highest form of love but doesn't know if a human can do that for her. dislikes the smell of lavender.

Ophelia, along with Aito and Serenity appear both on HEARTKNOT and in the HKRE. Since they are the public faces of 3HEART, they are also selected to appear in many different experiments and simulated worlds.

Iroha Aito - Aito, (sometimes referred to as Iroha) is an abrasive, explosive and manic spirit of 3HEART. She is devilish, narrow eyed, often laughing and dripping in mischief and self induced joy. Hedonistic, and knows what she has to do for her idea of the better good. She is not necessarily well liked from her fellow sisters outside of 3HEART or HKRE. However, she is incredibly loyal and very serious about her devotions. She is a bit sycophantic, and some have seen through it, it could be seen as a means to an end. She's not interested in how anyone sees her other than the HEARTKNOT and 3HEART. Whenever someone does something wrong, if she finds out she will confront them, she's a fan of public humiliation and outward aggression. Some of her sisters think it's all a front to protect herself based on the fact Aito went through the same terrors as all the other girls, but only Aito knows if this is the truth. Aito has always been a bombastic personality, and the opinions on her are very black or white.. sweet or sour.
Aito used to be a student at Heaven's Institute, and used to be friends with Ruina, but unfortunately they had a bad falling out. This doesn't stop Aito from trying to connect with Ruina during experiments held at the facility or simulated world. It could be argued that Aito is seeking something more than friendship, but it is unclear is someone like her can be with just one.
In HKRE, Aito is quite similar in her behaviours in HEARTKNOT, she is dedicated to try to climb up the latter to get to the middle or highest level of the 01 foundation, and many other researchers there can tell this fact. Aito is close with Ophelia and Serenity. Friends with Honour, Astrid.
fact - aito likes eating strawberry shortcake, beer, and takoyaki. aito likes smoking indoors, knifes, violence, and the colour red. aito hates quiet spaces and bad music.

Serenity Chimet - Serenity, sometimes referred to as Chima; is a professional girl and is a member of the 3HEART group. Serenity loves opulence, beauty, art and bandages. Serenity doesn't have many personal relationships other than 3HEART, but it is not on purpose, she cares a lot about those around her; to the point that it can get annoying to Aito. Serenity underwent gruesome experiments much like Aito and Ophelia but it was much shorter than what Yuro and Keiro went through. Despite this, Serenity is still struggling to cope in many ways, and struggles with self injury and is often seen with bruises, scrapes, or patches on her body. Chima thinks she's not great at expressing her emotions or conveying how she feels properly in conversation. So, she just focuses on her tasks that she needs to do, and spends a lot of time in the temple (simulated world), or the laboratory academic wing (physical world). Chima used to be close with Maja, but they've drifted apart and haven't spoken for a while, She and Maja are similar in the fact they're reserved and somewhat independent, therefore they are often in the library at the same times. Chima is looking to reconnect with Maja, but worries that it may be impossible due to her HKRE occupation.
She was selected from Heaven's Institute to work at HKRE after an experiment that she endured, along with Aito, Ophelia, and more. Serenity is now one of the higher up researchers.
fact - chima, despite her reserved and poised demeanour, can't handle her alcohol. she loves gemstones, constellations and the aurora borealis. she likes mini marshmallows and sweet champagne.