Rika Shiguma/Relationships

Kodaka Hasegawa
Rika seems to have been greatly attracted to Kodaka since the day he "saved" her from a lab accident. Rika constantly asks to return the favor by giving her virginity to Kodaka, something that Kodaka objects to. She is the only one that likes Kodaka openly (although due to Kodaka's "density", he doesn't notice this, or at least pretends to), and despite claims of being physically attracted to Kodaka, Rika is quite obviously interested in him romantically.

Although Kodaka strongly opposes Rika's harassment and her attitude in general, he finds her quite cute, outside of her perverted nature, telling her (accidentally) that she is "right in his strike zone". However, whenever Kodaka praises Rika ever so slightly, Rika instantly reverts to her perverseness which often forces Kodaka to whine about her personality and makes Rika depressed.

Ironically, only Rika truly understands what Kodaka wants, along with the situation that is happening. When she confronts Kodaka with this, Kodaka feigned ignorance as Rika soon respects that and decided to be Kodaka's first friend in high school. Conversely, of all the Neighbor's Club members, Kodaka is the only one who notices the hard work Rika has put in behind the scenes to make the Neighbor's Club more enjoyable for everyone.

After the pair officially acknowledged their friendship, Rika and Kodaka's interactions continue even outside their clubroom, signifying their close relationship. Despite knowing who Kodaka's infatuation lies with, Rika seems to support Kodaka's wishes but it was also implied that Rika wanted something more from their friendship but it was never her priority at the time, hinting that Rika continues to hold romantic feelings towards Kodaka. Either way, Rika sought ways with Kodaka in trying to create a meaningful friendship between them whilst the two bonded rather frequently by manner of having lunch together and the two going on a 'friendly date' when Kodaka asked for Rika's help in improving his appearance and reputation among his school-mates. Needless to say, Rika is grateful for having been Kodaka's friend but her lingering feelings towards him can still lead her to situations like deliberately showing her nude body to Kodaka and then embracing him from behind in the mixed baths when he called her 'cute', but was still sensible enough to eventually apologize because of this.

Rika continues to pursue her close friendship with Kodaka, even after the latter has gained himself a girlfriend in the form of Yukimura.

Yozora Mikazuki
Rika's attitude toward Yozora can be expressed as respectful as she addresses her as "senpai" and tends to be quite polite and patient when Yozora demonstrates her ignorance in varying topics that concern manga, anime and games. Despite different interests, they often team up to trick and bully Maria and Sena, which proves that they have many mutual traits. Rika also seems to understand this and tries to slowly turn Yozora into her soul mate having similar tastes. An example was when Rika convinced her club-mates to watch a movie revolving around the gay relationship between two male club members. While Yozora initially protested against Rika and what she perceives as an obscene movie, after watching the movie, Yozora became a fan of Rika's taste of movie genre and allowed future showings of it in their clubroom. Yozora initially insulted Rika on her perversions but Rika soon returned it by confirming Yozora's insults and even added more perverted comments back to Yozora. Being unable to handle this, Yozora soon stopped insulting Rika and would even do what Rika told her to do.

Though in the end, Rika only wanted to befriend and be considered as Yozora's friend, showing genuine concern when she succumbed to depression and knowing about her strained relationship with her half-sibling.

Sena Kashiwazaki
Although Rika was perverted, at times she would be shocked and surprised to know that Sena could be even more perverted than her. Rika also seems to have a complex (like most of the girls) towards Sena's buxom body, and would then insult Sena the same way as Yozora. Like Sena, if someone mocks or made a fool of themselves on one of Rika's favorite (BL) games, Rika would also become angry.

Later on, Rika revealed that she somewhat admired Sena for being simple, while also being surprising and complex as a person.

Kobato Hasegawa
Although both characters do not really interact much, there was a time when Kobato became scared of Rika when the latter wants to know what color her undergarments are. It was eventually changed to more mutual terms as the series progressed.

Yukimura Kusunoki
Rika was the one who convinced Yukimura that she is a female. Like Kodaka, Rika respects Yukimura's decision of wanting to be a man and hence, has decided to refer to Yukimura as a guy, even after the revelation of her true gender.

Rika and Yukimura's relationship turned sour after the latter made herself the girlfriend of her best friend, Kodaka. Though not entirely out of envy, Rika's contempt towards Yukimura lie when the two had an argument in regards to separating romance from her friendship with Kodaka wherein Yukimura called out Rika for being delusional. Rika, meanwhile, insists that she cannot get along with Yukimura for being too 'girlish'.

Maria Takayama
Rika almost never interacts with Maria except for when she is angered. In this situation, Rika follows the antics of Yozora and begins to trick and mess with Maria. Other times, Rika seems to treat Maria fairly normal.