Karoku Arumerita (嘉禄 Arumerita Karoku?) is the person that Nai is looking for.
Manga spoilers beyond this point.
In the Smoky Mansion arc (ch. 32-35), Nai and Gareki ended up inside a controlled alternate dimensional "garden". The figure greeting them inside this "garden" appeared to be Karoku, but when Nai went to hug him, Gareki realized there was another Karoku lying unconsciously on the ground. Gareki warned Nai to get away from the Karoku he was hugging. The standing Karoku claims to have Karoku within him and wanted Nai to come to his side.
Gareki shoots at this (Kafka) Karoku in order for them to grab the unconscious (Circus) Karoku and get away from this "garden". Back on Circus' ship, (Circus) Karoku eventually wakes up (ch. 38-39), but appears to have jumbled up memories despite being diagnosed as someone with his memories fully intact. It's presumed to be some kind of defense mechanism according to Akari, who's treating him. Since Karoku could not remember Nai, he instantly treated Nai like a complete stranger. Karoku could not even remember his parents' real name due to his mixed up memories.
// This bio is a work in progress. Will return back shortly to finish this. //
It was then revealed that he is the "original" Karoku.
He is described by Nai as a gentle person, and has acted thus so far after the recovery of his memories. During the disorder/confusion regarding his memories, however, he had acted cold and aloof, ignoring Nai and even going so far as to hit him because of the headaches he gets when Nai stirs his memories. This shouldn't be attested toward his real personality, however, as he had been suffering from the effects of his trauma. He likes Passing the Time and Enjoying the Nature.
He calls Nai his "special child", and is shown to have a deep connection with him. It has been revealed that Karoku is Nai's "creator" as the latter is one-half niji. He acts as an older brother of sorts, and has been watching over the younger since his creation. He's shown to be highly protective of Nai, as displayed through his hostile willingness to attack anyone who comes near him in later chapters, due to an injury sustained in the forest of Niji.
- The "Ka" in his name means "applaud, praise, esteem" and "roku" means "fief, allowance, pension, grant, happiness".
- Likes passing time enjoying nature.
- He is a bit saddened that Nai doesn't spend so much time with him anymore (as shown in a side-comic) and Jiki comments that his face was a "shocked expression as if his child just left the nest..."
- It is revealed by Nai that their home in the Niji Forest was constructed by Karoku and that he would always fish for their food.
- Karoku is a capricorn like Akari.
|Circus||Nai • Gareki • Yogi • Tsukumo • Hirato • Kiichi • Jiki • Tsukitachi • Iva • Karoku Arumerita|
|Kafka||Uro • Palnedo • Karoku|
|Research Tower||Akari • Ryoushi • Azana • Murano • Isosa • Tamon|
|Kuronomei Academy||Tsubame • Ranji • Shishi • Sesiri|
|Varuga||Mine • Derumen • Nima • Meiga • Kagiri • Kiharu|
|Defense System||Hitsuji • Usagi • Yukkin|
|Other||Erishuka • Yotaka • Tsubaki • Jingu • Kana • Tokitatsu • Kiripon • Yanari • Rissun|