For those of you who thought Hikari was well-to-do, well, it seems the authors here have taken the idea and ran with it. The "Hikari" (name not revealed) of Pokémon Special is a 5th generation descendant of a famous 200-year-old Sinnoh family, Berlitz. They are not only rich, but have a long tradition of scholarship. She even wears a pearl ring on her right hand, and a diamond ring on her left.
As for Pearl and Diamond (for some reason the name goes in reverse order), well, it seems there has been a bit of a mixup.
You see, the Berlitz family has a tradition of going to the peak of Mt. Tengan to obtain the material to make an ornament bearing the family crest... on their own. However, the butler, Sebastian, convinced Hikari's father to hire two bodyguards to accompany her. One of them will be wearing a red scarf, and the other, a green scarf. Also, Nanamakado takes the opportunity to do some research, and has three Pokédexes, three Pokétches and the starter Pokémon delivered to "Hikari" - one set for her, and one set each of her bodyguards.
Now, as luck would have it, Diamond and Pearl are wearing a red scarf and green scarf respectively. On top of that, when they collided with Nanamakado, they picked up the envelope containing rendezvous details for the bodyguards instead of the envelope containing their prize, a one-week free pass on the bicycle course at Masago Park.
As a result, Pearl and Diamond meet "Hikari". The duo believe that they are on some kind of reality TV show. "Hikari" believes that the duo are her bodyguards, and that the fact that they are more or less the same age as her is a "camouflage plan". She has her doubts though - not unreasonable considering the fact that the duo took 30 minutes to take care of the Mukkuru swarm. Meanwhile the real bodyguards wait patiently in Masago Park...
A defining moment for "Hikari": Pearl grabs her shoulder and tries to get her name. "Hikari" smacks his hand away and says: 「下じもの者に気安く名のってはならないとじいからいわれています。」 "Sebastian [who she refers to as じい] says that I must not tell my name to the people of the lower classes."
I have to say, Pochama suits her perfectly. Also, the characterisation of Pearl is more or less the same as Jun - impatient, in a rush. Naturally, Pearl is the tsukkomi, and Diamond is the boke.