Right now, I'm getting into romance that's like....the people aren't supposed to fall in love because they're hiding some deep dark secret. (Best if it was something like they had to kill each other...xD)

For example, what I'm reading now...: Superior

Mirai Nikki - I highly recommend it 😀

Kiss in the blue
Ao no Fuuin <- old school art, but the plot matches your expectations, especially with the kill each other part 🤣
Crying Freeman <- or at least the beginning, a hitman & his victim-to-be
First Girl ( especially the later volumes )
Kagen no tsuki
Vampire Girl <- kinda...
Sanctuary <- yakuza+female police officer
Suki ni Natte mo Ii no? <- kinda...one party's dark secret is revealed after some time.
Love SOS <- a manhwa, hope it's ok with you?
Royal Seventeen <- smut alert
Shoujo Ningyou <- smut alert
Seimaden <- this manga is simply made of such romances 🤣

I'm currently really annoyed with Vampire Knight, but I think it could match your expectations.
Without the dark secrets part, but with a lot of "killing each other"
: Basilisk.

[img]http://img.userbars.pl/69/13603.gif[/img]
Still the [color=red]bad[/color] cop.

Koi Kaze

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Thank you for the suggestions! I'll look through them now.