They can start by observing the new world's culture. Just like when we travel to a new place in our world, the OC can watch how the people interact, what their values are. For example, if the new world values honor above all else, the OC can try to uphold that in their actions.
One idea could be that the OC discovers they have a special power in the new world that is key to saving it from an ancient evil. For example, the power to control time, which is a very cool concept.
The new world could be a medieval - style realm filled with knights, castles, and magic. Percy might find himself in the middle of a war between kingdoms, using his skills to survive. Maybe there are mythical creatures like dragons and unicorns there.
Well, it could be really exciting. The OC might find themselves in the middle of all the action and drama in the RWBY world. They could form unique relationships with the different characters. Maybe they'd team up with Ruby and her friends against the Grimm. And in the harem aspect, they could have some interesting romantic or friendly interactions with multiple characters, like Weiss, Blake, and Yang.
It could be a powerful wizard or sorcerer in the new world who sees Ichigo as a threat to his rule. Maybe Ichigo's presence disrupts the balance of power that this antagonist has carefully maintained.
One possible plot twist could be that Ichigo discovers he has a special power in the new world that is completely different from his Soul Reaper powers. For example, he might be able to control the elements, which would change the way he approaches challenges.
Percy would first use his combat skills. If he's in a dangerous world, he'll rely on his fighting abilities. He might also try to find allies quickly. After all, he's used to having friends around in his own world.
There are often the brave and resourceful protagonists. They are the ones who get transported with the aincard and have to find their way in the new world. They usually have some kind of special ability related to the aincard.
Another plotline could involve the aincard having some sort of special connection to the magic or power source in the other world. Maybe it's the key to unlocking a long - lost magic that can save the new world from a great danger. The character then has to figure out how to use this connection while also dealing with the cultural and social differences of the new world.
One popular 'transported to another world novel' is 'Sword Art Online'. In this story, players get trapped in a virtual world. Another is 'Re:Zero - Starting Life in Another World' where the protagonist keeps getting sent back in time in the new world he is transported to. 'That Time I Got Reincarnated as a Slime' is also well - liked. The main character is reincarnated as a slime in a different world and has to build his own existence there.