Minoru

Unmarked spoilers. When Hideki could not figure out Chii's programme (even with the help of his best friend - Shinbo Hiroshi), he is referred to Minoru - a genius in the area of persocoms. So Hideki goes to find him at this huge house. Everyone expected an adult (supposedly older than Hideki), but we are presented with a 12 year-old boy instead. After hearing Hideki out Minoru helps him in any way he can, suspecting that Chii is the legendary Chobits.

Minoru, being an expert when it comes to persocoms, naturally has persocoms of his own, and yes, custom-made (all sanctily-dressed except for one). The one persocom to note would be Yuzuki.

Yuzuki was designed according to Minoru's older sister - who had passed away from illness. Minoru input all possible information he could of his sister into Yuzuki. Her looks are also similar to his sister, Kaede. Kaede also appeared in Angelic Layer (another series by CLAMP).

As the story continues, Minoru helps out Hideki along the way with Chii. But like many of the human-persocom relationships, we see the relationship between Minoru and Yuzuki develop too. At one point Yuzuki feels inferior because her abilities are limited (such as locating who sent the pictures) but Minoru doesn't blame her. He has a pained look whenever she compares herself to his sister. Near the end of the manga, Minoru tells Yuzuki that he doesn't see her as a replacement for his sister but as herself.