Tetsuwan Birdy

Both are anime from the 1990's. While Birdy the Mighty does not have masculine females, both titles do have females that can kick ass and have a lot of top notch action. 

A boy is saved from death by a girl through extraordinary means, in the process linking the two of them together. These OAVs don't share a ton in common beside this plot point/premise, but if it sounds appealing to you you'll probably enjoy both of these, as they're rather good. 

The entire time I was watching Parasyte the Maxim all I could think of was Birdy the Mighty. Both series have this aspect of alien/mutants who wear the skins of human race. Both series in turn have the same element of monsters who eat humans. Both are pretty dark and action packed border lining that of a horror series. In the case of Birdy the Mighty, the main character who is a male has a brush in with death, by the main character female who is an alien warrior of sorts trying to hunt these monsters among men, in her mission she accidentally kills the boy having to fuse her consciousness and body with his. He wakes up thinking its all a dream until she makes herself known, with one twist she can take over his entire body. He of course has to balance normal everyday life in school and family while keeping her a secret. As they also battle insane mutant monsters. (just simply describing this is a lot like describing Parasyte the Maxim.) Both are amazing series that have captured the good, bad and ugly sides of human vs monster. Both are dark and horrific at times. Birdy the mighty was on of those "cartoons" my parents bought for me as child because they thought it was only a "cartoon". Incidentally it was scarier then most horror movies I had managed to sneak and watch as a child. Watching Parasyte the Maxim for me was like a blast from the past redone, remastered, and downright amazing. I haven't laughed, cried, and be genuinely so focused and made to feel uneased by a show in a really long time. I couldn't take my eyes of it. Highly recommend both. read more 

Both are light hearted sci-fi action shows that have a similar feel with an adorable overpowered protagonist beating up aliens or robots or aliens in robots.  

Both are sci-fi action anime from the 1990's. Both are action-packed anime with similar animation. Both anime feature a strong female main hero that kick ass going to another planet to track a dangerous alien life form that is a major threat to the galaxy.  

Format is very similar, Unassuming boy gains a super powered alter ego due to alien influence and battles various monsters, while discovering the bigger picture. Guyver is just darker and more violent, also instead of the main character turning into a Woman, he turns into biological battle armor.  

Short OVA series about a badass alien girl who has to stick around with a geeky human boy.  

Very different settings, but both feature a lot of similar themes. Both feature a lot of top notch action, sci-fi elements (way more of this in BGC, cyberpunk included), and very strong female leads. Birdy herself could probably take on the whole squad of Knight Sabers! Both shows also balance in the action and plot with a good deal of humor and it works really well. All topped off with really top notch production values, these are really good examples of classic OVA's. 

Both have alien girls with normal slightly geeky high school earth boys. Birdy the mighty is a bit more "serious and dark" but still comical at times 

Your classic 90s hero fighting monsters on Earth. The first few minutes of Tetsuwan Birdy reminded me so much of the Guyver OVA series --- dark mood, the music, everything. If you've seen one of these shows, then make sure you check out the other. I can guarantee you'll love it.