First of all, I'm saying that this series is more realistic given the character development between the characters. What this series does right is creating a diverse cast of characters and implying realistic problems that people in real life having to face making them more likable.
There are 3 (4 pairings in the novel) pairings shown in the series. Each with their quirks and flaws.
Nostalgia (Takano/Ritsu) is the main pairing of the series. They revolve around the Belligerent Sexual Tension
couple you see in a lot of romantic comedies. However, with a slice of life added into this type of pairing you get a rather heartbreaking tale of two people who could not communicate well in the past and are trying to make up for it in the future despite the errors of the past.
Domestica (Hatori/Chiaki)...I have a lot of problems with this pairing but it's mainly about two childhood friends that have been together forever...except Chiaki is the definition of being an idiot and oblivious to love
and you would expect the usual forceful seme on a stupid uke...but Hatori is much darker than your typical seme when you add slice of life to this pairing and you get a yandere
that seems to turn the pairing into a Masochism Tango
or worse Domestic Abuse
and throws in the third person who suffers from both of them as a result of trying to be the nice guy
of the two.
Erotica (Yukina/Kisa) is more interesting than most because this is probably the first uke that actively pursues sex instead of being oblivious. Kisa comes off as the most realistic character in the series with fears that hits close to home and that the only thing that prevents him from your realistic character in the series is having the "fairy tale prince" Yukina to sweep him off his feet. They have the most stable relationship in comparison to the other two pairings listed above and only have to work with realistic problems like work and the age gap.
The last recent pairing is called Trifectia (Kirishima/Yokozawa and similar to Erotica they also have a slow, stable relationship that makes you root for them.
Overall, pick your favorite pairing and enjoy the show...then again...I ill advise Domestica given the Unfortunate Implications
surrounding the pairing but that's me being biased.