Tenshi Kinryouku

The relationship between the characters is similar. A gender-bender situation occurs in both. 

Very similar stories and very similar art. Although Angel Sanctuary is a bit more profound and complex than just good fighting evil, it's basically the same story: Main character had a different gender in his/her previous life and ,being born again among humans, is bound by a twisted love that contradicts his present existence as human. 

Both animes have a lot of similarities, specially the main character. They are both male, but on previous lives they were always women, although neither of them remembers about their previous reincarnations; they are supposedly very strong and their presence is crucial in the upcoming battle. Although Setsuna and Yuki have different personalities, they easily gain the love and friendship of the people around them. On both animes we have a battle between “good and evil”, although not always is clear who the real good/bad guys are. We find out about the real motives as the story progresses. I found the animation very similar. In Angel Sanctuary the colors are brighter but some characters are very alike and convey a similar feelings. read more 

Both being dark and broody gothic styled stories with an intricate artstyle as well as character design especially too and romance being one of its big plot points as well. 

in both anime the main story is that an angel has materialised within a mortal person. both have similar drawing and the same feeling in general, when watching it. 

They both involve siblings who run away from their parents and deal with supernatural celestial entities. The overall atmosphere is very similar too. 

I felt like doing some recommendations because they were really helpful for me so now it is my turn. So these anime has these things in common: *Both drawing styles are similar *Brother loves sister, sister loves brother... *They both have problems with angels And realy the feeling is the same because the boy is madly in love with his siter and he wants to protect her and than comes some badass angels... 

Winged bishies and apocalyptic theme 

Both Angel Sanctuary and X are dealing with earth's issue. The story shows a man who's against his own destiny and spends time fighting it. The two characters seem to be egoist at first but make real sacrifices for others. 

Both are broody and dark shoujo as well as quite a bit of action as well as both having visual kei and mythology inspirations to it as well. And also very intricate art as well too and character designs especially. 

Both are ovas with incest and tragedy.  

Both are OVAs centring around the forbidden attraction between a brother and sister in a highly dramatic and angsty fashion. Although Angel Sanctuary has the whole apocalypse thing to divvy the plot's attention between, its focus on the earliest parts of the manga allows the forbidden love component to take nearly as big a role as it does in BokuImo. 

Both have supernatural storytelling as well as also a ya cast and elements of romance in it and nice art and character designs too. 

Both are angel themed shoujo series with a mc with supernatural powers as well as also lots of nice art and character designs and fun to look at action as well too.