Kimi to Boku no Saigo no Senjou, Aruiwa Sekai ga Hajimaru Seisen

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. 

Both anime have the protagonists who are on the opposite sides of the spectrum, working together to stop the war once and for all. 

Because they are of the fantasy genre that share a similar premise and setting. Even though both shows setup a fantasy world with two divided factions at war with one another, the story focuses more on a Romeo x Juliet type romance. Two characters, one from each faction, trying to find peace or some common ground are also ordered to fight their adversaries. However, after their fateful encounter, these “enemies” grow fond of each other; becoming friendlier and more open with each other after each meeting. Even so, they have to live up to their duties as enemies destined to defeat the other. Both shows primarily focus on romance, but they also have similar mix of action, magic, fantasy elements, & slice of life moments.  read more 

A forbidden love! 

- Both anime is romance related - Iska and Kirito are both the "Black Swordsmen" of the anime - Alice and Asuna are the female protagonists that the male are deeply in love with Although Sword Art Online has a bad reputation, you have to admit the idea/concept of the anime was actually good. the first half of Sword Art Online was good but fell apart in the second half, it was redeemed again in the movie Ordinal Scale and the 3rd season the Alicization Arc. That is the gist of the recommendation 

In general both animes are a bit flat and nothing unique at the surface level. Main character is ridiculously OP. They each have a harem, but honestly they're just here to focus on their end goal. Great music and a nice light anime to watch. Seiyuus, staff and directing is on point. Also, minimal cliffhangers. Still enjoyable. 

Although 'Our last crusade or the end of the new world' tries many different things, including action and romance, one of the biggest take away I have watching it is the plot, the settings and how it's presented, all of which remind me of Acca 13. To be more precise, they're slow paced, they discover new environnments as they go and both protagonists try to attain world peace. I'm not saying that you'll enjoy one if you like the other, so be careful. 

Both of them are about enemies who falles in love with eachother and they are almost the strongest soldier in the army. 

While Grancrest is not about forbidden love there is large percentage of the show dedicated to romance. It's also a romance with lots of fighting with main male character and main female character taking part in the fighting. Also, the main character's feel similar in some aspects to main character's in Kimi to Boku no Saigo no Senjou, Aruiwa Sekai ga Hajimaru Seisen. Trust me if you liked Kimi to Boku no Saigo no Senjou, Aruiwa Sekai ga Hajimaru Seisen, there's a good chance you will like Grancrest. 

Futuristic setting. War between two nations that has been raging for generations. Barely anyone still remembers what even started the fighting. There is no clear distinction between which side is good and which is evil. 

Although they don't flaunt their skills, the main character is a potential threat to anyone and everyone near them although they don't have any malicious intent. In fact, both seem to have a slightly naive energy about them and a pure/optimistic goal ahead of them. Female lead provides adamant support when they're not fighting the main character off the battlefield. Great potential for character development, but their catchphrases get old quick. Would recommend both although they aren't high-priority shows. 

Male lead is OP, a little dense, and a bit of an "ostracized one" for being different despite having close knit friends. Female counter part is a tsundere, but craves male lead attention. Pretty character design and great music. Pretty same energy and if you can get past the "Onii-san" and "ISKA!", then it's actually enjoyable. 

I'm surprised this wasn't already recommended. Both characters get introduced as "Former" wielders of a specific blade. Romance aspects are involved, however Chrome Shelled Regios has a more Darling in the Franxx Lore. 

Both anime have the protagonists who are on the opposite sides of the spectrum. They both have a female and a male who are in opposite side of a war that been going on for decades, they are also working with each other to try and unite there homeland to make there respectful place peaceful without wars among each other. 

If you like Ikki and Stella you would probably like the couple in this anime either, but it isn't as good as Rakudai, though i think you will enjoy.