Iriya no Sora, UFO no Natsu

While Iriya has a much lighter tone through the first few eps, they both share a similar premise and similarly heart-wrenching developments. 

Estórias complexas, porém repletas de conteúdo. Personagens cativantes. Prosseguimentos interessantes. ---------- Stories complex, but full of content. Captivating characters. Continuing interest. 

both have girls that deal with military services,both are very deep stories.... 

Both anime shows the war and strong female character which have to save the world. Both have similar endings. 

The first few episodes of Iriya no Sora are slice of life, but the last ones have the same premise of "little girl is/drives a ultimate weapon and is the last hope against the enemy" 

The main character of both by chance meets a young lady who is very ill. Despite the fact their time with the girl is short lived they make the most of it and fight for her to have the best memories to the bitter end. 

The relationship between main characters and its development are quite similar, as well as overall mood and atmosphere. So, if you like one of this anime mainly for its drama part and mood (and not the setting, because they are absolutely different), there is a high chance, that you will also like the other one. 

Two great short series that I enjoyed watching so hence this recommendation. The similarities of these two anime involves: - thrilling drama - pacing - tragic love - light toned comedy - tense/touching scenes - bittersweet - emotional  

The main female is fighting against aliens who are attacking earth and they both have a guy they like very much and that they want to protect at all costs. 

The setting and the atmosphere are quite similar. Both anime are really touching and leave strong feeling of melancholy in the end. Also, they both have great soundtracks, that perfectly matches their mood. 

Similar story - girls gets to fly a spaceshuttle, boy stays on earth. 

Both feature sci fi conspiracy settings and a bioweapon female character, who is robbed of her dignity and interest as a character to be thrown into a cringey immature otaku fantasy love triangle with a totally average, lame male MC. The love triangle takes up way too much of the series' focus, undermining the sci fi plot, at times even totally contradicting the ostensible statements the sci-fi half of the story is trying to make about how human beings should treat one another. Kind of surprised that only one other person made this recommendation, the stories are almost exactly the same (except Elfen Lied is much more coherent and interesting). read more 

In the middle of summer, a high school boy without any particular traits meets a girl who arrived from outer space.