~~~The anime presents a unique romance concept, but it may not appeal to everyone. I still find the focus on sharing saliva strange and almost gave up watching due to feeling uncomfortable, but I ended up being captivated by Urabe's personality. Although my experience improved as the anime progressed, I felt it ended with a slight sense of "I expected more." Still, it's a good romance, and maybe one day I'll read the manga to get the full experience.

The art style, although not the most refined, effectively complements the story's "unique" nature. It's important to note that this is a 2012 anime, so don't expect an animation showcase. The character designs, despite being set in a school environment, are quite distinct from one another. The characters are well-developed, especially around the protagonists. I truly felt that they have genuine feelings.

Unique concept, the exchange of saliva as part of the romantic bond is unusual and creative, setting it apart from other romance anime.

Authentic characters, Urabe and Tsubaki have distinct and well-developed personalities, with a genuine relationship.

Gradual romance development, Although slow, the romance is built meaningfully with touching moments.

Exploration of unique themes, explores themes of intimacy and connection in an unconventional way, challenging norms and offering a different perspective on romance and human relationships.

As flaws, I can mention the repetitive focus on the "saliva fetish." The central premise of exchanging saliva may seem intriguing at first, but for some readers, it can become repetitive or even tiresome. Luckily for me, it was strange in the beginning, but I got used to it after 3-4 episodes. However, it's important to point out that this could be an issue for those who are sensitive to the topic or for those expecting more varied development. There is some development in the romance beyond the saliva, but don't expect too much of it.

For those looking for a dynamic and fast-paced romance, this might not be the best choice. The romance here is slow but quite meaningful to the story. However, if you're after something fast, this isn't for you.

~~~I would give Nazo no Kanojo X a 7/10. While the concept is unique and the relationship between the main characters has genuine and touching moments, the repetitive focus on the saliva fetish might turn off some viewers. The slow pace of the romance, although significant to the story, might not appeal to those looking for something more dynamic. However, for those who can get past the "strangeness" factor, there is an interesting romance story with simple but effective art.