Yu (Homunculus)

Yu is the named given to a homunculus by Mikaela, where both are characters in the world of the Seraph of the End series. Existing in the prehistoric past, Yu the homunculus was around with Mikaela during the era when dinosaurs roamed the Earth where they were seen in a seraph civilization.

Appearance
The most distinct feature about it was the single large eye in the centre of its being. While the sclera was white, both the pupil and iris were dark in coloration. Additionally, it was a spherical based entity. Capable of appearing in a smoke like form, like other homunclus it could also appear as a more solid ball. For what its skin was made of, it was dark in coloration but able to reflect light and refract it in parts.

Personality
Partaking in a game of hide-and-seek, Yu the homunculus awaited Mikaela to find it as it hid inside a living lizard. Apparently excited, it communicated this non-verbally by bouncing around before Mikaela.

Sentient and also able to read basic and advanced words, the homunculus had also read information that Sika Madu was hiding from Mikaela. For all the exceptionally sensitive information Yu has access to, it does not reveal it to others right away if ever. The same applies for when it can seemingly make out that Yu and Mika are in the area. When it outright can see Yu and Mika within a memory it makes no mention of this to Sika Madu who is alive in the present time and who can also access past memories.

History
Although not seen, Yu the homunculi was hidden inside a small lizard amongst some trees. Upon being found by Mikaela, the homunculus flew out the lizard's mouth when it was opened. Animated, it bounced around in apparent excitement while Mikaela stated he knew right away where it was hiding. When Mikaela spoke for it to come since father was calling, the homunculus was on his shoulder and flown towards a smoking mountain in the distance.

Within the seraph civilisation, Yu is levitating beside Mikaela with its gaze fixed on the ice cream he is carrying. Rather than placing itself on his shoulder, this time Yu flies upwards with him through the air. They both make their way to an opening in the side of the very tall and thin building rising from the seraph civilisation far up into the sky. While doing this, Yu is looking ahead to their destination.

At the reported top floor of the Tower of Babel, the homunculus floats slightly above Mikaela as he greets his father Sika Madu. Ever-silent as they speak, the homunculus physically reacts to being spoken to by Sika Madu after hearing that it was told by him to keep an eye on Mikaela. Its name mentioned by Sika Madu, it is close to Mikaela who is joyful that it has been given the name Yu and takes to looking at him. From Yu the homunculus' perspective it regards Mikaela's happy expression.

Observing Sika Madu as he details that naming a thing could curse them with a heart, it appears to listen further as Mikaela hears he was named by his father to curse him. While Mikaela has taken to embracing Sika Madu and seeks to clarify that he is joking, Yu the homunculus' gaze turns to something else. To the side, the homunculus is able to discern that Yu and Mika are present in this scenario.

After Mikaela has fallen ill, the homunculus looks at him as he kneels on the floor. It watches both Sika Madu and Mikaela as they discuss how they would each feel upset at the current situation of illness. It draws closer to Mikaela when he is happy to head to the cleansing room and goes there with him.

Within a room at some location, the homunculus floated over and looked in Mikaela's direction as he rested his head on Sika Madu's lap. It maintained its position over the bed they were on as Mikaela and Sika Madu spoke about going outside, and when going on a picnic was mentioned. Its concentration was on them as the discussion took place.

Watching Sika Madu leave the room, the homunculus then looked to Mikaela who was happy to speak about the picnic. When Mikaela said that it should come with them too, the homunculus considered this for a moment before having an expression of uncertainty.

When Paimon entered the room and meant to attack Mikaela with a knife, the homunculus acted first and moved itself in the way. Positioned in between them to protect Mikaela, the homunculus was struck by a light based power from Paimon and sent crashing into the wall.

Story
Where Yu and Mika exist in the present time they have established themselves in the Sea of Trees around Mt. Fuji where they mean to access past memories. This memory of the prehistoric past is one able to be accessed. Like them, this particular homunculus appears unique among others of its kind, along with Mikaela and Sika Madu, in that it is able to also detect their existence.

Powers and Abilities
Seemingly having the power of possession, the homunculus could enter and conceal itself within a living being. Its ability to form itself into a shadow based substance likely enables it to conceal itself within a smaller entity such as a lizard. While it could hide itself visually from Mikaela, it did not display the capabilities of being invisible to other senses he had. Naturally airborne, it is presumed that like others the homunculi could carry itself through the air at various heights and distances.

From within its lizard host the homunculi could apparently use it to stare in the direction of something it could see. Its ability to perceive things made it the only being from the prehistoric past to be able to make out that Yu and Mika were within the Tower of Babel with them. Other homunculi in the seraph civilisation did not show this ability to be able to perceive viewers from the far future.

Mikaela
Having been tasked with observing the First's son, Yu the homunculus went along with his escapades such as playing hide-and-seek and acquiring ice cream with him. Close to Mikaela, it would rest on his shoulder as they returned home together. Yu the homunculus would focus on the ice cream Mikaela had as well as regard him with a similar apparent fondness. Having been given its named "Yu" by Mikaela, it allowed itself to be handled and squeezed by him. Where Mikaela did not like the cleaning room, Yu went there with him. When Mikaela was assailed by Paimon, it acted to protect the former from attack.

Sika Madu
At some point, the homunculus had received a directive from who would be the future first progenitor of the vampires. At being spoken to that he was told to keep an eye on Mikaela, the homunculus reacts yet does not look at Sika Madu. Apparently hearing everything the First says to his son and understanding it perhaps better than Mikaela, this homunculus had also apprently read the information the First had tried to conceal.

Yūichirō Hyakuya
Sharing a first abbreviated name, the homunculus could apparently perceive this human member of the Moon Demon Company who lives in the present time.

Mikaela Hyakuya
A person turned demon who physically resembles Mikaela, the homunculus sees but does not act on his presence in the memory.

Paimon
This angel attempted to murder Mikaela and the homunculus did what it could to defend him.

Trivia

 * First seen in chapter 123, the shadowy eyeball being would have its species name revealed as a homunculus in chapter 125. Further, this specific homunculus would be named Yu.
 * Not specified whether it is the same, but the eye existing within Yu's memories has also witnessed events Yu can recall.