Warning! Spoilers ahead for Kaiju No. 8 chapter 12 and Attack on Titan chapter 139!
Within the span of 52 chapters, Kaiju No. 8 already fixed a massive flaw in Attack on Titan that the latter series didn't even attempt to address until the last two installments of its 139 chapters, namely, what was going on between Eren Yeager and Mikasa Ackermann.
What started out as ardent hope among Attack on Titan fans that something would happen between Eren and Mikasa quickly dissipated into smoke when it became abundantly clear that they were purely platonic. Ever since the day when Eren first saved her as a child, Mikasa ostensibly just devoted the remainder of her existence to pay him back in kind, mostly by using her incredible skills with omni-directional mobility gear to protect him against Titans. But then in the final two chapters, their true feelings suddenly surface at the worst possible moment. After beheading Eren in the final battle, Mikasa kisses his decapitated head ionately and in the alternate world of the path, Eren confides to Arwin that he doesn't want Mikasa to move on from him. It's everything fans wanted, but the fact that it was revealed at the 11th hour just made the entire concept completely random and forced. It just didn't feel real.
Kaiju No. 8's mangaka Naoya Matsumoto has already avoided this potential trainwreck through the portrayal of his characters Kafka Hibino and Kikoru Shinomiya who are the series' equivalents to Eren and Mikasa, respectively. Kafka can transform into his world's eponymous monsters like how Eren can become the Attack Titan. Meanwhile, Kikoru is an incredibly talented fighter who can't transform herself but can stay toe to toe with Kafka even when he's a kaiju much like how Mikasa can keep up with Eren as the Attack Titan through her prowess with the omni-directional mobility gear. But rather than completely ignoring even the concept of romance like in Attack on Titan, Matsumoto puts at last the prospect of it at the center of Kikoru and Kafka's relationship.
The romantic elements in Kaiju No. 8 are effective because Matsumoto chose to make Kikoru a stereotypical tsundere. What fuels Kikoru's hotheaded and harsh personality is her pride and arrogance at being one of the best fighters. And the fact that Kafka, besides his ability to transform, is incredibly weak, he is oftentimes on the receiving end of her temperamental tirades. But when Kikoru first sees him become a kaiju, she begins to develop feelings for him, most likely because his confidence skyrockets as a result. The first giveaway is in chapter 13 when, in the middle of a battle, he just complements Kikoru on her abilities and her pulse increases, which, of course, her specialized suite mentions out loud for everyone to hear much to Kikoru's horror. The fact that she struggles with how much stronger and more capable he is as a kaiju only makes her feelings for him more compellingly dynamic. And, of course, this causes Kikoru to unleash her inner tsundere with even more reckless abandon to shield her true feelings.
Although Kaiju No. 8 is still relatively new and is years away from catching up to Attack on Titan in of length, mangaka Naoya Matsumoto has already avoided the prospect of creating an ending where the true feelings of his characters are revealed in an unconvincing way. It's clear how Kikoru feels about Kafka, and even though readers aren't sure where Kafka stands on the matter, the fact that romance already plays a major role in the series as a whole means that when they do arise, it won't feel random or forced.
