acota

I read it sometime last year but I can't remember the name.

Here is what I remember

• The female protagonist is in love with the popular male protagonist (Super self centered) and he treats her like a slave
• They have been friends since they were kids
• They were in a group of 6 kids ( 3 male 3 female)
• The four older kids have vanished and they are trying to find them
• On their 15 or 16 birthday they transform into these gate keepers (The male is heavens gate the female is hell)
• The male forced his transformation
• The girl got sick on her birthday and didn't complete her transformation
• She can't control her other form nor remember what happens after she transforms
• She is super powerful after she transforms 
• I know two of the other characters are human and beast gates
• Another one of the characters loves the female protagonist while the male cares about someone else (though he started to sway from what i remember

It was a really interesting manga but I haven't been able to find it or find out if it was completed (It was around 10 or so chapters when I read it)

Please help! Thank you