 If you liked
Shingetsutan Tsukihime
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 ...then you might like
Kara no Kyoukai: The Garden of Sinners
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Manga adapted from novels written by Nasu Kinoko, the founder of Type-Moon. Both features protagonists named "Shiki" who has the ability to see the lines that symbolize the death of a thing and allows them to "kill" that thing. Both has supernatural, romance, and thriller genre. There might be some similarities of characters, too, like Tohno Shiki with Ryougi Shiki and Mikiya, Akiha with Azaka, etc.
Same multiverse, very similar concepts, different story and characters. The protagonits use eye power that lets them see the "death" of things thanks to which they can destroy practically everything. There are personalities named Shiki and SHIKI that are presented as kind of same but also kind of opposites. The dynamics between the protagonist and their love interest is also similar.