Infant

"I can clearly see into a person's heart: their weaknesses and frailties...I know just what to do in order make one suffer, to feel sorrow or hate. This is all familiar to me..."

The  was Naraku's seventh incarnation, serving as the vessel for his demonic heart. By separating his heart from his body, Naraku gained virtual immortality. Once this connection is discovered, the Infant becomes a prime target for Naraku's enemies, as destroying the heart will destroy Naraku as well. Despite being released from Naraku in the form of a baby, the Infant is able to speak fluently and is extremely intelligent, his skills of planning and manipulation easily on par with that of Naraku himself. The Infant also has the unique ability to look into a person's soul and manipulate their darkest emotions to possess them.

After being released at Mount Hakurei, the Infant's primary objective is to find the last unaccounted for Sacred Jewel shard, as well as the Border of the Afterlife, where the shard rests. Eventually, however, the Infant is split in half during a battle with a monk named Shinsen. One half regenerated into the Infant proper, but the other half became the child known as Hakudōshi. The two share a telepathic bond, and after being given the Fuyōheki, a stone which masks demonic auras, the Infant conspires with Hakudōshi to create Mōryōmaru and overthrow Naraku.

During the story
Born in Mount Hakurei, the Infant was created to serve as the vessel for Naraku's physical heart while the human spirit of Onigumo was left behind as lumps of flesh. Since Naraku knew his heart would eventually try to betray him, he purposely created its vessel in the form of an infant.

Entrusted to Kagura, the Infant was taken away from Mount Hakurei; Kikyō attacked them. Before Kagura could retaliate, he told her that she was not the one to kill Kikyō; his ability to speak shocked her. When Kagura was resting from her trip, he informed her that Naraku had succeeded in killing Kikyō.

First Mission
The Infant later took control of the Lady of a mansion, ordering her soldiers to capture suspicious travelers in the area; it was all part of his mission to take control of Kagome for her ability to see the jewel shards. To ensure Inuyasha wouldn't trouble him, the Infant had Kagura use her Dance of the Dead to make a dead priest give a false story about Kikyō's whereabouts. Once she was captured, he tried finding darkness in Kagome's heart, but he was surprised by how pure it was; there had to be some negative feeling inside. The Infant soon discovered Kagome's jealousy towards Kikyō and successfully put her under his control. When they attempted to place a defiled shard in Kagome to permanently put her under his control, the Infant found Kagome was resisting his manipulation; she accepted her jealousy as proof she loved Inuyasha. Inuyasha arrived and rescued Kagome; the Infant told Inuyasha that so long as he harbored feelings for Kikyō, Kagome could still be manipulated. Being taken away, the Infant decided to sleep, having used up too much energy trying to control Kagome.

Second Mission
When Naraku learned from Mimisenri that the final Shikon Jewel Shard was in the border to the world of the dead, the Infant was taken by Kagura to temples inhabited by powerful priests. The plan was to kill the priests and read their souls as they departed from this world to find a way to reach the border without having to die. Confronting a priest that appeared to be more powerful than the others due to detecting his and Kagura's arrival, the Infant succeeded in having him fatally wounded. Glancing into the priest's soul, he saw a land shrouded in white mist; however, at that moment, he was split in two by the last of the priest's power. Kagura took the Infant's two halves to Kanna, who took the left half. The Infant regrew his right half while the original right half of his body grew into Hakudōshi, who continued his mission to find a way to the borderland for the final shard of the jewel. The Infant being split into separate beings was something Naraku had planned; now Hakudōshi could take attention away from the Infant, effectively keeping Naraku's heart safe from his enemies.

In Hiding
The Infant was entrusted to Kanna and Kohaku for care; they took him to a castle where a Lady had just had a still-born child; Kanna sucked out the souls of all the attendants to make the claim that the Infant was her child more real. He slept most of the time, effectively keeping the ruse from being discovered. However, Princess Abi attacked the castle, correctly believing it to have a connection to Naraku. The Infant was protected by his foster mother and the castle staff; however, Kohaku killed the staff under Naraku's orders to retrieve him. Kanna sucked out the Lady's soul and took him back. After that, he and Kanna hid in cave.

Kikyō's shikigami came dangerously close to finding him, but Naraku appeared before her and served as a temporary distraction. Naraku gave the Fuyōheki to the Infant, having stolen it from Gakusanjin; it would act as a sort of armor by masking his demonic energy. At this time, the Infant conceived an even more brilliant idea for protection; having Hakudōshi created a demonic golem to house him. This lead to the creation of Mōryōmaru. When Inuyasha's group had the crystals of Gakusanjin's demonic energy, which could lead them to him, the Infant telepathically instructed Hakudōshi to steal them. Mōryōmaru is then left for him to use as he pleases.

To strengthen Mōryōmaru, the Infant has it attack the priest Goryōmaru to increase its strength by absorbing him; however, Mōryōmaru ended up being sealed by Goryōmaru and taking the place of the priest's devoured right arm. The Infant and Kanna waited inside the temple until his armor could be retrieved. Hakudōshi later decapitates Goryōmaru, allowing Mōryōmaru to escape the seal and eat the priest. Hakudōshi takes him and Kanna to the stone ogre cliff, serving as bait for Kagura to lead Inuyasha's group into a trap. However, they both leave soon after arrival.

Kikyō later comes across the Infant and Kanna while traveling, having been tracking Mōryōmaru's demonic aura. He and Kanna jump off a cliff to evade her, having Mōryōmaru fly them to safety.

Betraying Naraku
In time, the Infant came to see that Naraku was nothing more than an empty shell without his heart; he believed himself and Hakudōshi to be the original. Because of this, he sought to take Naraku's place with Hakudōshi's assistance. However, sometime after he is placed in Mōryōmaru by Kanna, Naraku locks him up with Mōryōmaru in the Goryōmaru's form; the statues from Goryōmaru's temple keep him sealed behind a barrier. Kagura is ordered to guard him, but Naraku doesn't let her know the Infant is inside Goryōmaru. Naraku continuously sends captured demons to the Infant's armor in order to strengthen it. He and Hakudōshi manage to persuade Kagura to release him with the promise of returning her heart to her right before Naraku's destruction.

The Infant reveals his armor's true form and gives her Goryō urns to use bandits as a distraction to keep Inuyasha's group busy. Knowing that he needs Mōryōmaru to become more powerful if he is to try to replace Naraku, the Infant has Hakudōshi and Kagura attack Inuyasha's group and Kohaku for their shards. However, he is only able to get the one from Inuyasha's group; trying to take Kohaku's shard, he reveals that the boy has gotten his memory back. Kagura betrays them, revealing he's inside Mōryōmaru; this left him in danger of being destroyed by the barrier-piercing Adamant Barrage if where he's hiding in Mōryōmaru is ever found.

When Hakudōshi is sucked into the Wind Tunnel, the Infant shows no remorse for the loss of his twin. With the deaths of Hakudōshi and Kagura (who died from being poisoned by Naraku's shōki), the Infant was left own his own without any assistance with his plans. Lacking any offensive abilities of his own, the Infant was forced to rely solely on increasing Mōryōmaru's strength as he continued his plan to take Naraku's place.

Strengthening his Armor
The Infant sends out pieces of Mōryōmaru to find demons with abilities that hold potential for making Mōryōmaru stronger. A venomous demon ate a piece of Mōryōmaru's flesh, growing in size and power; however, Inuyasha slew it before Mōryōmaru could absorb it. An arm of Mōryōmaru ate members of a snake demon tribe, gaining their venom. Wanting to strengthen Mōryōmaru's resistance to attacks, the Infant revives the aquatic demon, Meiōjū, allowing him to regain the piece of his armor, which is the hardest amongst demons, to bring it back to full strength. He also uses Meiōjū as bait to also take the Diamond Spears from Tessaiga. Once he has all these parts, the Infant transforms Mōryōmaru into a much more powerful form. He makes the poor choice of insulting Kagura in front of Sesshōmaru, who succeeds in cracking Meiōjū's shell with Tōkijin at the cost of the sword breaking.

Kanna later finds him, claiming to have defected from Naraku. Surprised by the claim of Naraku's emotionless puppet, the Infant decides to read her so-called "heart" to see if she's being truthful. She tells him of twin demons (Kinka and Ginka) whose blood can strengthen Meiōjū's shell; though the Infant succeeds in taking Ginka, giving Mōryōmaru a stronger shell, Tessaiga absorbs Kinka and gains the ability to resonate the powers of the twins, breaking the shell apart. Enraged at being exposed to his enemies, the Infant released a miasma to keep Inuyasha away. The Infant made his escape, most likely having Mōryōmaru expel Ginka to avoid future repeats.

He also had Mōryōmaru eat a moth demon sent out by Naraku's final incarnation, Byakuya of the Dreams, also taking a Shikon no Tama shard from the young wolf demon Kai; however, he failed to get Kōga's shards.

Death
Having strengthened his armor to perfection, the Infant has Mōryōmaru face off with Naraku to take the Shikon Jewel from him. Naraku laughed at him for becoming a fat king inside his "castle" - Mōryōmaru, also revealing the reason he was an infant. Naraku was reduced to scraps of flesh, which covered Mōryōmaru in an attempt to swallow both it and the Infant inside himself. However, the Infant turned the tables on his creator, having Mōryōmaru pierce and swallow Naraku. He next proceeded to fight Inuyasha and Kōga, succeeding in capturing Kōga.

Since the fight was not going in his favor as much as he hoped, the Infant wondered why his armor hadn't gotten any stronger. Much to his horror, the Infant discovered the reason why was because Naraku was still alive and eating his armor from the inside-out. Trying to leave, the Infant was stopped by Naraku, who had eaten the barrier-piercing demon tree Yōmeiju; he was willing to die if it meant taking Naraku with him. However, Naraku fully absorbed Mōryōmaru, keeping the Infant trapped with Yōmeiju's vines. Almost sucked into the Wind Tunnel like Hakudōshi had been, the Infant lost the Fuyōheki, leaving Naraku unable to mask his demonic aura.

Personality
Usually, the Infant is calm; however, he is usually sadistic. He believes in being greeted properly, even before a fight. Being born of Naraku's heart, he knows full well how negative emotions can influence others, believing the desire to kill is contagious; the Infant believed Sango and Miroku would kill the guards simply because he ordered their deaths. He takes delight in toying with others' emotions; he taunted Inuyasha by saying Kagome's jealously towards Kikyō can still be used to his advantage. Like Naraku, he feels no remorse for any of his actions. As he is Naraku's heart, the Infant eventually sought to usurp him. When faced with the threat of being absorbed back into Naraku, the Infant was willing to die at Inuyasha's hands, showing he wished to have his own freedom, just like Kagura.

Physical appearance
As his name says, the Infant takes the form of a young baby. He has short, light violet hair that matches his eyes; however, his eyes lack pupils. His expression is usually blank, unless angered or joyful. When he was taken away from Mount Hakurei, he was originally wrapped in what appeared to be Naraku's baboon pelt. However, the Infant later gains a green kimono and a light blue blanket.

Powers & Abilities

 * Manipulation:  The Infant had the ability to search deep within a person's heart for darkness and if they didn't have enough willpower to resist him, they would be under his control. Once he's done with a puppet, they die.
 * Barrier Erecting:  The Infant can create a strong barrier, being able to make it large enough for himself (when inside Mōryōmaru) or for others. It can send attacks back at his enemies, just like Naraku's. Unlike Hakudōshi, this barrier is controlled by himself and not Naraku which the reason why Naraku has to obtain the power of Yōmeiju to penetrated it.
 * Shōki: After Inuyasha breaks Mōryōmaru's shell and he is rendered visible, the Infant released shōki to make Inuyasha back off and to make his escape. He only used this once, so it's unknown how potent his shōki is.

Trivia

 * Many English-speaking fans consider the Infant's true name to be, which is how other characters refer to the Infant in the original Japanese language version. However, akago is merely a Japanese word for infant, and is not really a name.
 * Interestingly, the Infant never speaks in the series after being split in half until after Hakudōshi dies.