Gai Tsutsugami is the mysterious and charismatic leader of the group "Funeral Parlor". A childhood friend of Shu Ouma and Mana Ouma, Gai is one of the protagonists of the first half of Guilty Crown, but he was later revealed as the main antagonist of the second half of Guilty Crown after his resurrection.
Gai is a fairly tall man with a bitch lean yet well built physique, light colored skin, long blond hair and blue eyes, almost looking that he is of european descent.
His typical attire consists on black pants, shoes and shirt, with a Funeral Parlor long coat, being black with a red middle strip. With this he also typically wears a military harness, where he holds his weapons such as grenades, flashbombs and a holster where he carries a weapon near-identical to an old school Luger P08 pistol.
After being resurrected, Gai now sports clothing very similar to the Anti-body uniform. He has also changed in colors, shown by the loss of pigment in his hair and skin. In addition, Gai also has an Apocalypse Virus crystal formation around the right side of his face and eye, with the iris of the said eye turning red, possibly a side effect of his infection.
He could be of Russian descent because of his facial appearance in general, but since his surname is Japanese, it would be unknown if he was Russian, but it could be clear of course since of his facial appearance.
Gai was first found by Shuichiro Keido, who used him and many other boys in his experiments to create an Adam for Mana. The experiments involved injecting artificially-enhanced samples of the Apocalypse Virus on several boys, of which Gai was among. Out of all test subjects, Gai was the one who better responded to the virus. At one point in fear he ran away for the facility, ending up falling into the sea and was found by Mana and Shu. He was nursed back to health by them, and lived with them. He fell in love with Mana and became best friends with Shu. Gai soon realized that Mana was infected by the Apocalypse virus and attempted to tell Shu of Mana's insanity. But Mana found him first and gave him a gun. By asking him to shoot the star on top of a Christmas tree, the bullet rebounded back at him. He later protected Shu, when Lost Christmas occurred. He later left to get stronger, at which Shibungi states that he met Gai as a child soldier in Africa.
He has a lot of charisma and is Shu's rival. He guides Shu who has the "Power Of Kings" and aims for a successful revolution. He also appears to be able to 'see' the Void that is inside of a person and is highly intelligent. He is a great strategist, able to create very complex plans that are able to predict people actions. He is manipulative as shown in episode 7, to get the Kuhouin group's support he manipulated GHQ to attack the ship, they were on. Then manipulated both Shu and Arisa to stop the missiles to show the "Funeral Parlor" abilities.
In episode 6, he reveals his arrogant, bold and cold personality is a front for the "Funeral Parlor". He takes the members deaths very seriously and thinks very little of himself, like Shu. But due to his manipulative nature, it is hard to question if it was the truth or a ploy to get Shu to join the "Funeral Parlor".
Gai has stated his reason to fight is to find a woman (later revealed to be Mana) and take her in his arms. After his resurrection he is a cold and ruthless man who shows no remorse against people he associated with in the past as he had no qualms severing Shu's right arm. He reveals that his role as leader of of the "Funeral Parlor" was just an act and their he of thought of them as his pawns as a King has no friends. However in the final episode he reveals that he played the role of a villain to stop Mana from resurrecting herself and Shu will be the one to stop them.
In Episode 1, Gai is seen showing up to fight the thugs who had attacked Shu and eventually scares them away. He comes up to Shu and asked him if he just abandoned Inori but before he could continue a huge explosion occurs. Someone then shouts out saying that the GHQ were attacking and they all head to the front lines. Gai asks Tsugumi how Ayase and the others were doing and she tells him that an enemy was coming at them from the left. After Ayase destroys it, Gai yells at Shu telling him to protect the Void Genome and runs off. Gai is later seen in shock at Shu's newly awakened power. After the battle (continuing in episode 2), Gai orders Shu to take Inori and bring her to him in fifteen seconds. They soon arrive there and before Shu could speak, Gai gets a call from Ayase. She apologizes to him for failing her mission but blushes when Gai tells her he's glad she was alive. He returns his attention to Inori who just woke up and tells her he was disappointed in her, saying the Void Genome was for his use. He goes on to explain what Voids are and tells Shu that he's not allowed to stand and watch by the sidelines. Before Shu can protest, Gai grabs him by his shirt and tells him that he can either be selected out of this world or adapt to it and change. He receives a call from Arugo, who tells him that the Anti Bodies have captured some people who were taking shelter in a building.
Gai meets with the rest of the "Funeral Parlor" and forms a plan to rescue them. After the plan starts, he reveals his identity to the GHQ before Guin starts a countdown and says that if they don't surrender he would die. However, Shu uses the Kaleidoscope to reflect the lazers back onto Guin, killing him and some other GHQ members in the process. Later, Gai offers Shu to come and work for the Undertaker but is turned down. In Episode 3, Gai reveals Undertaker/Funeral Parlor to the rest of the world and states his goals. He later informs Shu of someone who goes by the codename "Sugar" that witnessed the previous events that happened. He states that the only way to make the person forget is to extract their Void.
In Episode 4, Gai disguises himself as Shu's lawyer when he got arrested by the GHQ, in order to save Kido. When the plan went sour, Gai changes the plan and it ends up prevailing. After the battle Gai finally persuades Shu to join the "Funeral Parlor" and they set off.
Gai reveals Shu to the "Funeral Parlor" and orders Ayase to train him if she valued her life. He is later seen walking into a room with Inori and it is revealed that he has to take her blood two to three times each month, for an unknown reason. After, Gai sets the first part of his plan into action to take the Leukocyte, but this backfires when it attacks the area they were in. It kills all of Gai's teammates and Kyo so Gai decides to change their plan. While taking Inori's blood, Gai questions himself on why he was doing all of this, saying it took all he had just to keep up the 'leader' act. He is over-heard by Shu, and they get involved in a fist fight. Shu punches Gai to the face, knocking his chain off. He tries to reach for it but can't because of his injury. Shu picks it up for him and tells him that he'll help and Gai calls him an idiot. They carry out the plan to destroy the Leukocyte by using Kido's Void, before they are interrupted by Daryl who wants revenge because Gai humiliated him. Gai defeats him quite easily even though Daryl was in his Endlave, which Shu is amazed about. Gai is revealed to have known that Shu had the 'pen' that Segai gave him, and uses it to let the Leukocyte target him. However, Shu shows up with a new Void which was given to him by the girl that resembles Inori but Gai refuses to tell Shu who the owner of the Void was. They succeed and Shu tells Gai that they were both accomplices and Shu helps Gai up. After some days Shibungi informs Gai that they are running out of supplies,although they had still some savings they have no route to transport new supplies, Gai apparently knows someone who will help them.The next night Gai and Shu disguise themselves as Butler and attend a party on cruise ship to make a deal with the Head of the Kuhouin group (also known as Arisa's grandfather). Accidentally, Shu runs into Arisa, in which he tries to run away from her. He tells Gai to take care of the rest and flees. Gai stops Arisa before she could chase after Shu, and he tells her that she is like his armadillo pet that he had when he was young, which makes Arisa furious. She tries to slap Gai but he stops her by holding her hand. After Gai makes his proposal to Arisa's grandfather, Shu tells Gai that Tsugumi informed him about a attack on the ship from the anti-bodies. When Shu asks him what they should do in order to save the passengers, Gai tells him to meet him at the upper deck. Gai takes Arisa there and tells that he is about to cast a spell on her, and tells her to close her eyes. When she opens them, Shu draws out her void and they together successful defend the ship. Gai mentions to Arisa that she is actually very shy despite the tough image she gives out.
Gai goes to stop Mana from coming back to life and from Lost Christmas happening again, and helps Shu regains his memories. He finds out that Gai was his best friend when they were young, but went by the name of Triton.
After helping Shu rescue Inori, Gai goes to free Mana's soul from the pod containing it. However, the crystals protecting the pod end up mortally wounding him. Close to death and pinned to Mana's pod, Gai requests Shu to stab him through the heart at the same time, in order to break the pod and free Mana's soul. He dies embracing Mana, finally reunited with his lost love. A few weeks after the breakout, Shu, and the few who remain of the Funeral Parlor, still grieve about Gai.
It is later revealed that Haruka Ouma and the Anti-bodies have resurrected Gai. After Shu successfully destroyed the controller for the Ghost Unit, his allies turn against him, Shu falls down a hillside and soon after Gai appears in front of him and cuts his right arm to gain the King's Power. He also mentions to Shu that he was never a King to begin with, but only a usurper. Gai says that he always has been the King. Gai was a part of human trafficking when Shuichiro Keido took him in as his own son and experimented on him, along with other abandoned boys in a facility where they were given enhanced Apocalypse injections in hopes of creating another "Adam" - potential mates for Mana Ouma since Kurosu Ouma refused to have his children be a part of Yuu and the Da'at Society's plans. Fearing that he would eventually become a victim to the Apocalypse treatments, the young Gai fled from his imprisonment, chased by security dogs before falling off of a cliff and down to sea.
In Episode 22, he uses Mana's void to kill Shu for hurting her feelings once again only to let Shu use Inori's void from the flower that contained her spirit and defeated Gai. After the battle concludes, Shu starts to hallucinate and sees Gai standing in the middle of the utopia of Da'at (memories inside the crystals), Gai tells him about the role of natural selection and evolution, and that Da'at can simply reanimate Mana. Even if she dies, she will just come back; never free from the Apocalypse Virus, and the only way to only stop it is to fulfill her role of The Fourth Apocalypse. Gai then takes Shu to the church moments before the advent of Lost Christmas happened but this time, Gai hugs Mana and they crystallise together, thus freeing Mana from her role and fulfilling Gai's dream to take Mana in his arms. Gai then tells Shu to save Inori as he breaks down along with Mana.
Overall, Gai is one of the most dangerous characters in the series, both prior and after his acquisition of the Void Genome. His natural intelligence and charisma coupled with his combat skills, makes him a highly versatile and deadly individual. The effects of his resurrection together with his forced acquisition of the Power of the Kings, made him extremely powerful and even more dangerous, enough to single handedly destroy a large naval UN fleet with minimal effort.
Due to his advanced stage infection of the Apocalypse Virus as a result of serving as a guinea pig for the virus experimentation, Gai gained the ability to perceive other people's Voids, a skill he would later use extensively in his plans against the GHQ forces.
As the leader of the "Funeral Parlor", Gai is a highly intelligent individual and a skilled tactician, as most of the attacks made by the Undertakers are made under his command. One example is when he and Shu crashed the Kuhouin Group's cruise ship party to rally influential supporters against the GHQ forces; Gai had previously tipped off the GHQ to have them launch an attack while having Shu use Arisa's Void to successfully stop the attack, thus making a demonstration of the Funeral Parlor's power and gaining the Kuhouin Group's support. Due to his ability perceive other individuals Voids, Gai used this skill to great effect in the Funeral Parlor's missions by directing Shu on the most useful Voids to use to deal with each situation.
Aside from this Gai is a master manipulator, who due to his natural charisma and leadership skills is capable of inspiring unwavering loyalty and devotion onto the Funeral Parlor members such as Argo and Ayase among others or play Shu to his desires by using his attraction to Inori. He also deceived Daath into believing he had become an ally in Mana's revival, while in reality he only did so that he could have Shu kill them both so that the Daath couldn't use her anymore.
While initially not possessing any supernatural abilities like the Void Genome, Gai was well-versed in a variety of combat forms and has an extensive military training since childhood, where he served as child soldier in an African battlefield. Shibungi, one of people he was meant to kill and latter becoming his right-hand man, noted that Gai had a natural talent. His skillset includes extensive strategic and tactical planning (being the overall planner for the Funeral Parlor's attacks), infiltration and stealth (mascarading as a lawyer to enter a GHQ facility to save Shu), firearms and marksmanship (capable of using several weapons such as pistols, rifles and RPG's with precision), and hand-to-hand combat (using a variety of moves such as swift kicks, open-handed strikes, throws and body locks). He is more than capable of easily outmatching and killing multiple GHQ/Anti-Body soldiers and in one occasion even destroying an Endlave piloted by Daryl, a highly-skilled pilot in his own right, with nothing more than a simple pistol by moving onto it's head and shooting it in a key point on the head.
Gai possess great physical abilities such as strength, speed, reflexes and endurance. His physical prowess appears as near-superhuman on some occasions; As a young boy, he was able to survive a brutal attack by a pack of dogs and falling from a large cliff into the ocean and in his older years he was somehow the only survivor from the blast of the Leukocyte satellite with only minor injuries. Gai is also very fast and nimble, at one point being capable of outmaneuvering an Endlave in a one-on-one situation. After his resurrection, it appears as his raw physical strength grew as he was able to effortlessly wield Inori's large Void with one hand to slice off Shu's arm, before he or anyone else could react or even understand what happened.
In episode 17, Gai gains the Power of the Kings after cutting off Shu's right arm, causing the Void Genome to bind itself in Gai's right arm instead and giving Gai the power to draw out a Void: an object which is a person's inner psyche taking physical form due to the crystalization effects of the Apocalypse Virus.
In order to draw out a Void, Gai is required to make both physical and eye contact much like Yuu and Shu. However an individual still collapses due to this action, implying he hasn't fully mastered his powers. However he was able to bypass most of these shortcomings by using his own Void, the Leader's Rifle: a rifle-like weapon that could forcefully bring out a Void by shooting the respective individual with it.
In the short time he gained his powers however, he displayed fast growing skill in the combat use of various Voids, such as using Yuu's Void to capture Inori, and wielding Inori/Mana's Void, a massive broadsword, effortlessly against Shu. He has also shown the ability to combine Voids to create more powerful ones, which he uses to extremely deadly results, such as creating a missile that could not only destroy a stealth aircraft but also produce energy shields strong enough to block a flurry of bombs dropped by it or a large bow and arrow with enough power to nearly destroy an entire U.N fleet with one shot. His overall prowess with the Power of the Kings was on an equal footing to that of Shu and Yuu who arguably had much greater experience in Void use.