15 [Similar Anime] Like Mysterious Girlfriend X

Similarities:

The concept of scissors used by a main female protagonist is featured in both series. Not only that though, they seem to have a very odd relationship with the main male protagonist

While not entirely alike, both series features a strange female protagonist who one day meets the main protagonist in a bizarre matter; they also seem to have a strange relationship as the two characters are almost nothing alike.

In both series the male and female leads involuntarily get dropped into a girlfriend/boyfriend relationship. They are reluctant at first, but they slowly embrace their connection. In both series, the leads never been in a relationship or close to anyone, so they stumble to discover the mechanics of how a true relationship/love works, discover each others' and their own bodies and feelings through some very awkward, sweet and slightly ecchi moments.

+Both anime plot wierd and unclear
+Both have an unusual art style for anime these days
+Both about a silent guy and a realy weird girl
+Both are making "contract" between the guy and the girl
+Both are somewhat erotic

There's quite a few interesting similarities in both of these series to be honest and worth the watch:

Strange girlfriends, uniqueness, comedy, and drama. What else more could you want? Anyways, these two anime(s) are unique in their way of not only the story but the way it's played out. In both series, the protagonist meets a strange girl whom they eventually date and face other obstacles together. Both series has have hints of supernatural-like elements as well as being difficult to predict what happens next.

Both series features a protagonist who one day certainly gains a "mysterious" girlfriend.

Being so attached to her gives the most moments on how their chemistry is perfect for each other. Noticing that there's a spark that can light out of her mood. Pointing out where your hands reach on him as soon as you felt a geniune feeling that flows inside none other than your inner self.

Little bit diffrent, cause it's more mysterious girlfriend. The main protagonist here is boy than girl, so imagine Shouta percpective. Alot less drama-romance.

This recommendation may be a stretch, but these two series both gave me weird feelings while watching them. Mysterious Girlfriend X is more light-hearted and lovey-dovey while Mirai Nikki has more of a serious tone to the whole anime. Both series have their main characters obsessed over one another (Yuno and Yukki in Mirai Nikki, Tsubaki and Urabe in MGX). If you liked MGX, I think you should be able to like Mirai Nikki, and vice versa.

While Kuzu no Honkai (10/10) is much darker than Nazo no Kanojo X (10/10), they are similar in some ways:
Both have kind of a forceful/aggressive romance relationship.
Both female MCs are cute and weird at the same time and they also have dark and short hair.
Both have an interesting (uncomfortable for some) concept.
Both are Seinen and are not for kids (+17).
Both are School and Slice of Life.
Both have a dark vibe. While Nazo no Kanojo X's ambiance may not seem like it, some find the repeated sunset, night, rain and dream scenes in it kind of dark.

Both have a similar tone at times, and Urabe and Tomoko feel very similar. I have described Urabe as a Kuudere fusion of Tomoko and Ryuko (Kill la Kill) and think that gives an accurate preface to her character.
I loved both series in spite of them both being weird and unpopular.

Romance with a twist, these shows offer a spiced up new element to your average school romance. Out of the ordinary for sure however the unique qualities don't take away from the fun or romance of the show. If you enjoy one you should enjoy the other.

Nazo no Kanojo X and Sukitte li na yo both share a same general plot but told in two different artistic representations. Where Nazo no Kanojo X is a bit more fantasy due to the importance and connection between Urabe and Tsubaki through saliva, Sukitte li na yo's story is rooted more in a realistic representation on two people in school from different groups and different personalities can find a lasting love within each other. Both are tested throughout their own stories but both will leave you hopeful in the power of love.