This is a "Wild Mass Guess" entry, where we pull out all the sanity stops on theorizing. The regular entry on this topic is elsewhere. Please see this programme note.
The GALAX system will cause chaos and tragedy.
They are painting it as the greatest invention ever. Hajime says you can't rely on the Internet for everything, which could be Foreshadowing it causing havoc after becoming such a big part of everyone's lives. Which leads to the next theory:
Berg Katse is going to create chaos in GALAX using Rui's appearance.
They know each other but it isn't clear if they are working together. Berg may be manipulating Rui, or waiting for the right moment to impersonate him and hijack the GALAX system.
Rui mentions he picked 100 Super GALAX Users to give them access to the Crowds. As Hajime is G-101, these 100 people can be the Gatchamans around the world, farfetched as it sounds.
The question would be, if there are 101 Gatchamans and 100 chosen GALAXers, who is the extra? We have Hajime, who is #101 and different to everyone else in her team, but also Sugane, the only Gatchaman shown so far who doesn't use GALAX.
And tying with the first theory, if the GALAX system goes nuts, then the odd-one-out would be the only hope to save the day.
Jossed. The Crowds are regular GALAX users who Rui recruited. The 100 coincidence seems to be an Arc Number thing.
Subsequently; JJ will appear before him and put his note back into his body, before extracting his true one; Katze's extraction was flawed and Rui's not a true Gatchaman.
Rui is (unofficially) G-100
Katze's method of turning him into a Gatchaman seems to have been a bit different, but maybe whatever assigns the numbers decided he was 100 anyways.
G-100 will be plot relevant
Utsutsu is G-99, Hajime is G-101. We may also get some exposition on G-97 and G-98, as well as the Gatchaman between Jou (89) and Sugane (96).
Berg Katze's riddle.
Episode 8 hints it could be love. Hajime says it's what kids want, and O.D. compares Berg to a child.
O.D. and Berg Katze are related.
They may be siblings. Both are tall, extremely effeminate and flamboyant aliens (or half-alien, in O.D.'s case). O.D. also talks about Berg as if he knew him very well.
Or they have a similar relationship to Sugane and Jou. At the least, they seem to be from the same planet.
They also both have power beyond that of a normal Gatcha, and if we assume O.D. stands for something, they have the same two-name naming structure. They also both have red eyes, although O.D.'s eyes are less obviously red, possibly because he is half human. At the very least it isnt unreasonable to guess that O.D.'s non-human half is a similar or the same species as Katze.
Interestingly, according to the artbook on the series, O.D.'s design was originally meant to go to Berg Katze. Their relationship may be a bit of a remnant of that idea, with O.D. being connected to him in some way.