Kishuku Gakkou no Juliet

Both stories are in reference to Romeo and Juliet but in different methods. Both have characters fighting for opposite factions who fall in love and intrude on each other's daily lives and slowly introduce each support character as their relationship develops.  

Kishuku circles race vs race and Nisekoi is yakuza vs yakuza. Highschool students suppose having a childhood rivalry between protagonist and main love interest. Kishuku leans more of the "Romeo and Juliet" scenario while Nisekoi follows a different picture book. 

Characters from different factions with a long history of hatred slowly start to fall in love with each other. Although Kishuku Gakkou no Juliet's romance seems brews faster, Kimisen has a fantasy/magic element that the other does not have. 

It gives enemy lovers vibes. The characters also have the same hair color. Both are supposed to hate each other yet they get along so well. Both anime are set at school, and the romance is pretty similar.  

Both are Romeo and Juliet type of stories about forbidden love because both sides belong to opposing groups. Then you got the guy confessing first and both series are mostly a rom com where they date but try to hide it. 

Both loosely based on Romeo and Juliet by William Shakespeare Show rivalry between clans and the star-crossed lovers hiding their love from their clans. Kishuku Gakkou no Juliet is more on modern mixed with medieval and romantic comedy while Romeo x Juliet is more on fantasy and tragedy. Black Doggy Dorm - Montague Family and White Cat Dorm - Capulet Family Romio Inuzaka - Romeo Montague and Juliet Persia - Juliet Capulet Juliet is more of a fighter.  

The show LACKS the mindgames of Kaguya sama, and It's pretty straightforward from the start, so If you liked Kaguya Sama mainly because of that, the show is not for you. BUT, the soul of the show is the same: -A superromantic couple who love each other from the start (Here the couple is dating secretly though) -Same ratio of comedy/romance -> While the relationship gets closer and closer with a moments of real sweetness from time to time, the 80% the show is comedy (Kaguya sama is gold comedy while Juliet is silver comedy, but It's the same gags out of nowhere/ plans of the main cast which always end up in a unexpected comedy twist). -The dynamic of both MC and MainGirl is so similar as well.  read more 

Both Shows have a Boy and a Girl from two different countries Falling in Love with each other and having a relationship after a duel with each other. In Both Shows the Girl is the daughter of a Noble, while the Boy has Family issues. They also try to keep their realtionship a Secret from the public. 

While both animes are polar opposites in which one of them is dating for real but have to keep it secret and the other one is fake dating but have to pretend that they're a real couple, the humor is similar because both involve having to hide the secret and a lot of spicy shit happens when the secret gets leaked to the wrong people. Both series have some girl who blackmails the MC and the MC must do her bidding.  

The main couples are madly in love with each other but for some reasons, they have not been together yet. Bocchan suffers from a deadly curse that he can't touch Alice while Romio and Juliet get separated by political conflict.  

Both show are very similar in the aspect of divided love. In each show the male and female protagonist are separated by some "societal divide". Whether that be another country or a another world, each protagonist loves the other, and is willing to do anything for them. 

If you like the stories of Romeo and Juliet, GUNDAM: THE 08th MS TEAM may interest you. It's 'Romeo and Juliet with Mechas'. The boy is a Mecha pilot of the army that defends the Earth... and the girl is a soldier from the faction of humans who live in space that attack Earth. They will face an impossible love. It is a spin-off of the Gundam saga so it is not necessary to have seen any other anime from that franchise.  

Boarding School Juliet and Vampire Knight share a theme of clandestine romance amid societal discord. In the halls of Dahlia Academy, the forbidden love between Romio and Juliet, representing the Black Dogs and White Cats respectively, mirrors the societal challenges faced by star-crossed lovers. The animal themed factions, akin to the day and night divisions across humans and vampires in Vampire Knight, serve as symbolic barriers, highlighting the struggles of love in the face of predetermined conflicts between opposing hierarchies. The black and white uniforms in both series act as visual metaphors for class divisions, with each shade further embodying the stark contrasts that their relationships must persevere through never ending strife. While there is a playful lighthearted rivalry which adds a touch of humor, the dormitory segregations help to accentuate the prohibited nature of these quarreling factions. Despite their differing atmospheres, the two anime use the visual language of cheeseboard uniforms and split architectural divisions to poignantly illustrate the complexities of love amid national and interracial strife. read more 

Both of them have a couple that has different origins and try to go against the society to stay together 

Both main male MC's express themselves genuinely in a refreshing manner compared to other romcom's. Romio is best girl 

Both are Romcom that make me laugh and make my hearth racing. They have a strong protagonist with a girlfriend and a "harem". Yamada is a school life but with a bit of magic but it's modern, it's not a common romcom ( indeed that's my favorite). And in yamada, there is no secret relationship with a war beetwen people like in Juliet. Have fun watching it !