CR chart kind of thing
Dropped characters have their name completely in gray.
sync
Although Sync is about the closest thing to an "ally" that Erika has in Damned, the two of them have a terrible relationship. Sync led Erika to the Coliseum solely for his own entertainment and he thinks very little of her. In turn, Erika resents having to keep him in her good graces because he's a pretty useful tool with very useful things that she would love to take off his hands. Though their relationship started with mutual blackmail, at this point, Erika only hangs around him because, despite the circumstances, he happens to be the only person who would go willingly with her anywhere and is one of the few eligible parties who can explore certain parts of the Institute with her.
At the very least, they can both get a kick out of trolling Guy.
the trickster (gabriel)
If it weren't for the need for a fourth party to enter the Coliseum, Erika would have had nothing to do with Gabe. Unfortunately for her, he was her opponent in the Coliseum and it seemed like the detective's authority wasn't quite powerful enough to trump the grace of God. To say Gabriel killed her would be a bit of an understatement. To say that they both are not on speaking terms would also be an understatement.
Despite that, Erika was able to get some petty revenge by eating a cupcake in front of him, so she feels a little better about being gutted like a pinata. Unfortunately for Erika, her adventures with Gabriel are far from over.
scott pilgrim
Though she does not know his name, nor the reason why, Erika has reasoned that Scott Pilgrim was the one who threw orange juice at her hair during the food fight. Because he ruined her beautiful hair, she is now committed to destroying his life.
Well, that's what she says, but so far, she hasn't done much other then have a pillow fort war with him. Their first battle ended in a cease-fire under threat of military intervention from an outside power, so for now, her revenge has to wait.
But she's still rather mad.
peter parker
Although Erika has yet to meet Peter in person, and she does not actually know who he is, she does know that someone was being an insufferable white knight and attempted to convince her not to destroy Scott's life when she left a warning message for him on the bulletin board.
Erika has decided that this person will pay for ruining the experience of leaving a warning on the bulletin board and she has made it her other mission to find out who he is and ruin his life too.
rita mordio
Rita has proven herself to be not an idiot, and for this, Erika quite likes her. The two met after the Shadows event and had a discussion that involved lots of thinking about what sort of trick was used to produce the illusions, and Erika marked her down as someone to meet up with in the future for more discussions.
She is unaware that Rita has mistaken her first name as "Furudo", but would probably find it extremely amusing if she ever figured it out and wouldn't bother to correct her.
guy cecil
Erika enjoys triggering Guy's gynophobia and otherwise has a fantastic time tormenting him, even though she's only done it twice. Unfortunately for Guy, Erika came to realize that he and Sync were well acquainted, and he has become a figure of even greater interest to her.
So she will be trolling him for a long, long time. Recently, she's learned that he went through the Coliseum at some point from deductive reasoning and confirmation from Sync, so she may still have some business with him in the future. Assuming she can corner him again, because that's abut the only way she'd ever be able to get him to talk to her.
nigredo (???)
Nigredo was part of the Coliseum team that Erika formed, as the group's only kidnapped member. Despite spending two nights in the same group, Erika never bothered to learn his name and the only noteworthy interaction they had was Erika duct taping his mouth shut while trying to treat some of his wounds, as she needed him alive at the moment. After her basement adventures, Erika was more then happy to never see his face again. They did end up talking again, but it seems like he has no interest in her beyond the fact she was still alive and maybe a slight curiosity about her resemblance to Rika Furude.
As for what Erika thinks about him, the fact she has yet to bother asking for his name probably says enough about how she feels about him.
jessica drew
Erika's third roommate thus far. Since Erika believes she will go the way of the other two, she hasn't spoken much to her roommate other then to give her some information about how Damned works. As Jessica had just arrived when they met, Erika asked for her dog tag and only knows her as "Julia Carpenter", which won't change anytime soon.
Erika is quite aware that she and "Julia" aren't going to get along anytime soon, so she isn't exactly interested in trying to break the ice with her either.
aigis
Aigis is an odd girl to Erika, if only because she demonstrated the power of Persona to her personally to heal her wounds. Though the sight was pretty bizarre for the detective, it became even more bizarre when she realized she knew exactly how Aigis's power was being suppressed, as well as the implication that her powers were legitimate. There are still other strange aspects about Aigis that Erika wants to investigate in the future, but her power is the most obvious one.
Aigis was very grateful that Erika chose to return Yukari's Evoker and she offered her help to Erika, if the girl ever needed it. Erika, being the kind of person she is, will certainly choose to take Aigis up on that offer at some point in the future...
yukari takeba
Erika's second roommate. As Erika missed a good opportunity to question her first roommate, she was much more talkative with Yukari, though she doesn't feel the need to keep an eye on her roommates and generally stays out of her affairs.
However, Yukari did have the distinct "honor" of getting to hear Erika's newest theories about the Institute, after she gathered her evidence for the day. Although one can't really say that the two of them got along swimmingly, Erika didn't have any particular problem with her roommate either. That was because Yukari is a heavy enough sleeper that she doesn't notice Erika creeping at the foot of her bed every night.
When Yukari disappeared, she left behind her Evoker, which ended up helping Erika despite it being completely useless to her. For that, Erika is the slightest bit grateful for her roommate.
battler ushiromiya
Battler Ushiromiya was Erika's rival and opponent at the end of Episode 5, as he replaced Beatrice as the Game Master of Rokkenjima. However, in Landels, it came to an ugly surprise to Erika when the Battler she met had no memory of this: In fact, he claimed that the fifth game hadn't even finished. He also claimed that the Golden Witch Beatrice, whom she had destroyed, was alive and well, but Erika never found any evidence of that and dismissed it in front of him. Though she tried to keep tabs on her hated enemy, other pressing matters and the large population at the Institute keep her from creeping on him as much as she'd like to. Eventually, she lost track of him period and has simply assumed he, like many others, simply disappeared from the Institute.
lion ushiromiya
She hates Lion for existing. Literally, Lion's existence justifies the "man from 19 years ago" excuse that ultimately lost her the 5th game, so she really does not like Lion despite the fact they only spoke once. Unfortunately for her, it seems like Lion has also disappeared from the Institute, so she never had the chance to ask any questions... not that Lion would have told her anything.