If you liked the Hadi Girl manga, the Anime-Planet community thinks you'd like:
Both series revolve around an easily embarrassed girl who has never been in a relationship before and who is now forced into a relationship by someone else. Both series give off similar "awww" feel and stuff, so you can't go wrong with one if you liked the other.
If you're into those awkward girl romance series, then you're in for a treat. Both Kyou no Yuiko-san and Hadi Girl are such manga and both are quite good at it too. If you don't know what I'm talking about, know that this type of character is sort of like a tsundere, except with the tsun-tsun side and violence being replaced by shyness and awkwardness.
Both series feature a female character who is labeled as perfect (looks, grades etc.), but who is also often misunderstood (has difficulties interacting with peers). Both of those gals try to enter a relationship with a quite normal guy, but they find romance much more difficult than studying and get embarrassed very easily. If you liked one of those manga then the other one should prove to be a good read too.
Yuuto the otaku loves two things more than anything: moe, and artwork by Sayane, the teen's favorite online artist. So when the boy is offered a part time job at a local anime shop he eagerly accepts, unaware that there, he'd run into the beautiful Kotone, an 'otaku hater' who's never given Yuuto the time of day! With newfound commonalities, the two quickly become good friends – but little does Yuuto know that Kotone harbors another secret, one that will blow his mind!
Both Hadi Girl and Tonari no Kashiwagi-san are those awkward high school girl romance series. In both, the female lead is super shy, but everyone gets fooled by her false front and believes that she is very cold. The main plot line revolves around her being pushed into a relationship with a guy. If you liked one, odds are, you'll like the other one too.